Optical fiber connector, optical fiber connector assembling method, fusion-spliced portion reinforcing method, pin clamp, cap-attached optical fiber connector, optical fiber connector cap, optical fiber connector assembling tool, and optical fiber connector assembling set

ABSTRACT

An optical fiber connector includes a ferrule, an inserted optical fiber, an external optical fiber, and a pair of reinforcing members that pinches and reinforces a fusion-spliced portion of the other end portion of the inserted optical fiber and the front end portion of the external optical fiber. The reinforcing members include adhesion layer on the inner surface thereof which comes in contact with the other end portion of the inserted optical fiber and the front end portion of the external optical fiber. The adhesion layer is depressed at the position where the inserted optical fiber and the external optical fiber come in contact with each other so as to closely adhere to the outer circumferential surfaces of the optical fibers in the fusion-spliced portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application based on U.S. patentapplication Ser. No. 13/548,927, filed Jul. 13, 2012, which is acontinuation based on a PCT Application No. PCT/JP2011/050560, filedJan. 14, 2011, whose priority is claimed on Japanese Patent ApplicationNo. 2010-006290 filed Jan. 14, 2010, Japanese Patent Application No.2010-006292 filed Jan. 14, 2010, and Japanese Patent Application No.2010-006331 filed Jan. 14, 2010, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical fiber connector assembled toa front end portion of an optical transmission medium such as an opticalfiber cord or an optical fiber cable and a method of assembling theoptical fiber connector, and more particularly, to an optical fiberconnector in which a front end portion of an optical transmission mediumis optically connected to an optical fiber (short optical fiber)inserted into a ferrule by fusion splice between optical fibers, amethod of assembling an optical fiber connector, a method of reinforcinga fusion-spliced portion of optical fibers which can be suitably usedfor the optical fiber connector, an optical fiber connector assemblingtool, and an optical fiber connector assembling set.

The present invention also relates to an optical fiber connectorassembled to a front end portion of an optical transmission medium suchas an optical fiber cord or an optical fiber cable, a pin clamp usedtherein, and a method of assembling the optical fiber connector.

The present invention also relates to an optical fiber connector capwhich is detachably attached to the housing of an optical fiberconnector when assembling the optical fiber connector to a terminal ofan optical transmission medium such as an optical fiber cord or anoptical fiber cable in which an optical fiber and a fiber-like tensilemember extending along the optical fiber is covered with a sheath andwhich is used for assembly work of the optical fiber connector.

2. Background Art

In the past, an optical fiber connector having built therein amechanical splice mechanism interposing an inserted optical fiber, oneend of which is fixed to a ferrule and an optical fiber of an externaloptical transmission medium, between two divided parts in a state wherethey are butt-jointed to each other and maintaining the butt-jointedstate was known as an example of an optical fiber connector enabling awork of assembling an optical fiber connector to an end portion of anoptical transmission medium such as an optical fiber cord or an opticalfiber cable to be carried out on a splicing site (for example, seeJapanese Unexamined Patent Application, First Publication No.2002-196189).

An optical fiber connector connecting an optical fiber of an opticaltransmission medium and an optical fiber built in a ferrule of theoptical fiber connector to each other by fusion was also known (forexample, see U.S. Pat. No. 5,748,819 and Japanese Unexamined PatentApplication, First Publication No. 2008-65315).

Japanese Unexamined Patent Application, First Publication No.2002-196189 (particularly, paragraphs 0022 to 0024 and FIGS. 1 to 4)discloses an optical fiber connector precisely positioning opticalfibers between two divided elements having an alignment groove (a Vgroove, a U groove, or the like) used to align optical fibers andbutt-jointing the optical fibers.

U.S. Pat. No. 5,748,819 (particularly, FIGS. 1 to 3) discloses anoptical fiber connector having a structure in which a fusion-splicedportion is disposed in a slot formed in a ferrule, a front end of abuilt-in optical fiber is located on an end face, and a rear end of thebuilt-in optical fiber is exposed into the slot so as to befusion-spliced to an end of an optical fiber of an optical transmissionmedium in the slot.

Japanese Unexamined Patent Application, First Publication No. 2008-65315(particularly, paragraphs 0033 to 0036 and FIGS. 3 and 4) discloses anoptical fiber connector in which an end of an optical fiber of which theother end is fixed to a ferrule is fusion-spliced to an end of anoptical fiber core and the fusion-spliced portion is reinforced with areinforcing member such as a heat-shrinkable sleeve or a metal sleeve.

An optical fiber connector configured to splice an inserted opticalfiber of which an end portion is fixed to a ferrule and an optical fiberof an external optical transmission medium to each other by fusion orthe like was known as an example of an optical fiber connector enablinga work of assembling an optical fiber connector to a front end portionof an optical transmission medium such as an optical fiber cord or anoptical fiber cable to be carried out on a splicing site (for example,see Japanese Unexamined Patent Application, First Publication No.2002-196189 and Japanese Unexamined Patent Application, FirstPublication No. H10-319275).

An example of such a type of optical fiber connector is a multi-coreoptical fiber connector (an MPO type optical fiber connector; MPO:Multi-fiber Push On) defined in the JIS C5982 or the like.

When butt-jointing the optical fiber connectors to each other, a guidepin protruding from a joint end face of a ferrule of one optical fiberconnector is inserted into and locked to a guide pin insertion hole of ajoint end face of a ferrule of the other optical fiber connector.Accordingly, the ferrules are positioned with a high precision.

One optical fiber connector is of a male type having a guide pin and theother optical fiber connector is of a female type not having a guidepin.

The guide pin is inserted into a guide pin insertion hole formed in theferrule and then the rear end portion thereof is supported by a pinclamp formed in the back of the ferrule.

When assembling an optical fiber connector to an optical fiber cordterminal extending a tensile fiber has been carried out, which islongitudinally added to an optical fiber of an optical fiber cord and isreceived in a sheath along with the optical fiber, to a cord terminaland to fix the tensile fiber to the rear end of the body (housing) ofthe optical fiber connector with a metal ring by swaging so as tosatisfactorily detain the optical fiber cord in the optical fiberconnector (for example, see Japanese Unexamined Patent Application,First Publication No. 2001-235656).

The optical fiber connector disclosed in Japanese Unexamined PatentApplication, First Publication No. 2002-196189 does not require analignment groove to position optical fibers relative to each otherbefore splicing. Accordingly, the decrease in cost is limited due to thepresence of components to be machined by high-precision processing.

The optical fiber connector disclosed in U.S. Pat. No. 5,748,819requires fusion work at a side surface position of a ferrule.Accordingly, when a general-purpose discharging electrode is used in thefusion work, the ferrule may be adversely affected and thus a generalfusion splicer should not be used, thereby making the fusion workdifficult.

In the optical fiber connector disclosed in Japanese Unexamined PatentApplication, First Publication No. 2008-65315, the other end of theoptical fiber fixed to the ferrule is drawn out from the ferrule, theadverse influence of the fusion work on the ferrule is reduced. However,since the reinforcing sleeve needs to pass the optical fiber coretherethrough before the fusion work and to move to a position where itcovers the outer circumference of the fusion-spliced portion after thefusion work, it takes much labor to form a splice reinforcing portion.The outer diameter of the optical fiber core needs to be smaller thanthe inner diameter of the sleeve (so that the outer circumferentialshape of the sectional surface of the optical fiber core is included inthe inner circumferential shape of the sectional surface of the sleeve).Accordingly, it is difficult to apply this technique to an opticaltransmission medium such as a drop cable or a multi-core optical fiberhaving a large outer diameter (outer circumferential shape).

In order to enhance the efficiency of the work on the splicing worksite, there is a need for an optical fiber connector having a structurecapable of selecting the presence or absence of a guide pin (male typeor female type).

In the optical fiber connector, the guide pin can be attached anddetached by inserting or pulling the guide pin, the rear end portion ofwhich is fixed to a pin clamp, into or from the rear side thereof.

However, it is not possible to avoid the increase in size of the opticalfiber connector, in that it is substantially difficult to attach anddetach the guide pin in consideration of the adverse influence on anoptical fiber spliced portion (for example, a fusion-spliced portion)and it is necessary to guarantee a space for movement of the pin clampbetween the ferrule and the optical fiber spliced portion so as to avoidthe adverse influence.

When the optical fiber connector is configured to weaken the fixingforce in the rear end of the guide pin and to be able to easily insertor pull the guide pin into or from the front side of the ferrule, thespace on the rear side of the ferrule is not necessary, but there is aproblem in that the guide pin can easily fall out with this structure.

When performing the work of fixing the tensile fiber to the body of theoptical fiber connector by swaging, it is necessary to swage a metalring in a state where tension is applied to the tensile fiber.Accordingly, for example, as disclosed in Japanese Unexamined PatentApplication, First Publication No. 2001-235656, a tool (hereinafter,also referred to as a swaging tool) capable of fixing the optical fiberconnector and the optical fiber cord and fixing the tensile fiberextending from the cord terminal is necessary. The labor of fixing theoptical fiber connector, the optical fiber cord, and the tensile fiberextending from the cord terminal by the use of the swaging tool isnecessary.

SUMMARY OF THE INVENTION

The invention is made in consideration of the above-mentionedcircumstances and has the following objects.

(1) An object of the invention is to provide an optical fiber connectorand a method of assembling the optical fiber connector, which canfacilitate the work of fusion-splicing optical fibers to each other andthe work of reinforcing the fusion-spliced portion.

(2) Another object of the invention is to provide an optical fiberconnector to and from which a guide pin can be attached and detached,which does not cause the guide pin to fall out, and which can suppressan increase in size, a pin clamp used therein, and a method ofassembling the optical fiber connector.

(3) Still another object of the invention is to provide a cap-attachedoptical fiber connector which can simply perform the work of fixing atensile member, which extends from the terminal of an opticaltransmission medium (an optical fiber cord or an optical fiber cable) inwhich an optical fiber and a fiber-like tensile member extending alongthe optical fiber are covered with a sheath, to a housing the opticalfiber connector without using a tool for fixing the optical fiberconnector, the optical fiber cord, the tensile member extending from thecord terminal and which can enhance the work efficiency of the connectorassembling work, a method of assembling the optical fiber connector, andan optical fiber connector cap.

To achieve the above-mentioned objects, according to an aspect of theinvention, there is provided an optical fiber connector including: aferrule; an inserted optical fiber of which one end portion is fixed tothe ferrule and of which the other end portion protrudes from theferrule; an external optical fiber of which a front end portion isfusion-spliced to the other end portion of the inserted optical fiber;and a pair of reinforcing members that pinches and reinforces thefusion-spliced portion of the other end portion of the inserted opticalfiber and the front end portion of the external optical fiber, whereinthe reinforcing members include an adhesion layer on the inner surfacethereof which comes in contact with the other end portion of theinserted optical fiber and the front end portion of the external opticalfiber, and the adhesion layer is depressed at the position where theinserted optical fiber and the external optical fiber come in contactwith each other so as to closely adhere to the outer circumferentialsurfaces of the optical fibers in the fusion-spliced portion.

The adhesion layer may be formed of rubber or an elastomer.

The adhesion layers of the pair of reinforcing members may closelyadhere to each other at the position where the fusion-spliced portion ispinched between the pair of reinforcing members.

The pair of reinforcing members may include protuberance portions andrecessed portions engaging with each other on both sides in the widthdirection perpendicular to the length direction of the inserted opticalfiber and the external optical fiber, and the state where the adhesionlayers of the pair of reinforcing members closely adhere to each othermay be maintained by causing the protuberance portions and the recessedportions to engage with each other.

A ferrule boot covering the surrounding of the portion of the insertedoptical fiber protruding from the ferrule may be attached to theferrule, and the pair of reinforcing members may clamp the ferrule bootat end portions thereof close to the ferrule.

To achieve the above-mentioned objects, according to another aspect ofthe invention, there is provided a method of assembling an optical fiberconnector, including the steps of: fusion-splicing the other end portionof an inserted optical fiber, of which one end portion is fixed to aferrule and of which the other end portion protrudes from the ferrule,to a front end portion of an external optical fiber; and preparing apair of reinforcing members including an adhesion layer, which can bedepressed at the position where the inserted optical fiber and theexternal optical fiber come in contact with each other, on the innersurface thereof which comes in contact with the other end portion of theinserted optical fiber and the front end portion of the external opticalfiber, pinching the fusion-spliced portion of the other end portion ofthe inserted optical fiber and the front end portion of the externaloptical fiber between the pair of reinforcing members, and causing theadhesion layers to closely adhere to the outer circumferential surfacesof the optical fibers in the fusion-spliced portion.

The adhesion layer may be formed of rubber or an elastomer.

When pinching the fusion-spliced portion between the pair of reinforcingmembers, the adhesion layers of the pair of reinforcing members mayclosely adhere to each other on both lateral sides of the optical fibersat the position where the fusion-spliced portion is pinched between thepair of reinforcing members.

The pair of reinforcing members may include protuberance portions andrecessed portions engaging with each other on both sides in the widthdirection perpendicular to the length direction of the inserted opticalfiber and the external optical fiber, and when pinching thefusion-spliced portion between the pair of reinforcing members, the pairof reinforcing members may be combined to maintain the state where theadhesion layers of the pair of reinforcing members closely adhere toeach other by causing the protuberance portions and the recessedportions to engage with each other.

A ferrule to which a ferrule boot covering the surrounding of theportion of the inserted optical fiber protruding from the ferrule may beattached is used as the ferrule, and when pinching the fusion-splicedportion between the pair of reinforcing members, the ferrule boot may beclamped between the pair of reinforcing members at end portions of thepair of reinforcing members close to the ferrule.

A first reinforcing member having a shaft portion at an end portionopposite to the ferrule and a second reinforcing member opposed to thefirst reinforcing member may be used as the pair of reinforcing members,an assembling tool including a reinforcing member holding portionholding the second reinforcing member at a predetermined position and abearing portion rotatably holding the shaft portion of the firstreinforcing member when pinching the fusion-spliced portion between thepair of reinforcing members may be used. Before pinching thefusion-spliced portion between the pair of reinforcing members, a stepof holding the second reinforcing member on the reinforcing memberholding portion, a step of placing the fusion-spliced portion on thesecond reinforcing member, a step of holding the shaft portion of thefirst reinforcing member on the bearing portion, and a step of rotatingthe first reinforcing member toward the second reinforcing member aboutthe shaft portion in the bearing portion until the fusion-splicedportion is pinched between the first reinforcing member and the secondreinforcing member may be performed.

According to still another aspect of the invention, there is provided areinforcement method of pinching and reinforcing a fusion-splicedportion, in which end portions of a first optical fiber and a secondoptical fiber are fusion-spliced to each other, between a pair ofreinforcing members, including the steps of: preparing a firstreinforcing member having a shaft portion at an end in the lengthdirection of the first optical fiber and the second optical fiber and asecond reinforcing member opposed to the first reinforcing member as apair of reinforcing members including an adhesion layer, which can bedepressed at a position where the first optical fiber and the secondoptical fiber come in contact with each other, on the inner surfacewhich comes in contact with the first optical fiber and the secondoptical fiber; preparing an assembling tool including a reinforcingmember holding portion holding the second reinforcing member at apredetermined position and a bearing portion rotatably holding the shaftportion of the first reinforcing member when pinching the fusion-splicedportion between the pair of reinforcing members; holding the secondreinforcing member on the reinforcing member holding portion; placingthe fusion-spliced portion on the second reinforcing member; holding theshaft portion of the first reinforcing member on the bearing portion;rotating the first reinforcing member toward the second reinforcingmember about the shaft portion in the bearing portion until thefusion-spliced portion is pinched between the first reinforcing memberand the second reinforcing member, and interposing the fusion-splicedportion between the pair of reinforcing members and causing the adhesionlayers to closely adhere to the outer circumferential surface of theoptical fibers in the fusion-spliced portion.

The adhesion layer may be formed of rubber or an elastomer.

When pinching the fusion-spliced portion between the pair of reinforcingmembers, the adhesion layers of the pair of reinforcing members mayclosely adhere to each other on both lateral sides of the optical fibersat the position where the fusion-spliced portion is pinched between thepair of reinforcing members.

The pair of reinforcing members may include protuberance portions andrecessed portions engaging with each other on both sides in the widthdirection perpendicular to the length direction of the first opticalfiber and the second optical fiber, and when pinching the fusion-splicedportion between the pair of reinforcing members, the pair of reinforcingmembers may be combined to maintain the state where the adhesion layersof the pair of reinforcing members closely adhere to each other bycausing the protuberance portions and the recessed portions to engagewith each other.

According to still another aspect of the invention, there is provided anoptical fiber connector including: a ferrule that has a guide pininsertion hole into which a positioning guide pin of an opposite opticalfiber connector can be inserted so as to be pulled out therefrom; anoptical fiber of which one end portion reaching a joint end face of theferrule is fixed to the ferrule and of which the other end portionextends from the ferrule; and a pin clamp that can be attached to aprotrusion protruding from the opposite side to the joint end face ofthe ferrule in the guide pin inserted into the guide pin insertion holeso as to be detached therefrom in the direction crossing the guide pininsertion hole, wherein the pin clamp includes a fitting recessedportion that is fitted to the protruding portion of the guide pin toregulate the movement in the length direction of the guide pin, and thefitting recessed portion is formed to receive and put out the protrusionof the guide pin in the direction crossing the guide pin insertion hole.

The protrusion of the guide pin may have a large-diameter portion and asmall-diameter portion having a diameter smaller than that of thelarge-diameter portion at the tip thereof, and the fitting recessedportion may be locked to the small-diameter portion to regulate themovement of the large-diameter portion toward the tip.

The ferrule may have two guide pin insertion holes, which are formed onboth sides with the optical fiber pinched therebetween, the pin clampmay have a bottom portion and side wall portions formed on both sidesthereof and a space surrounded with the bottom portion and the side wallportions on both sides thereof serves as an insertion space of theoptical fiber, and the pin clamp may have two fitting recessed portions,which are formed in the side wall portions on both sides.

The optical fiber may be an inserted optical fiber, the other endportion of the inserted optical fiber may be spliced to an externaloptical fiber, a ferrule boot covering a portion of the inserted opticalfiber extending from the ferrule may be attached to the portion, and thepin clamp may be formed to insert the ferrule boot into the insertionspace.

A holding protrusion that protrudes to the inside and that regulates themovement of the ferrule boot in the insertion space to the outside maybe formed in the side wall portions of the pin clamp.

According to still another aspect of the invention, there is provided apin clamp used for an optical fiber connector including a ferrule thathas a guide pin insertion hole into which a positioning guide pin of anopposite optical fiber connector can be inserted so as to be pulled outtherefrom and an optical fiber of which one end portion reaching a jointend face of the ferrule is fixed to the ferrule and of which the otherend portion extends from the ferrule, wherein the pin clamp can beattached to a protrusion protruding from the opposite side to the jointend face of the ferrule in the guide pin inserted into the guide pininsertion hole so as to be detached therefrom in the direction crossingthe guide pin insertion hole, wherein the pin clamp includes a fittingrecessed portion that is fitted to the protruding portion of the guidepin to regulate the movement in the length direction of the guide pin,and wherein the fitting recessed portion is formed to receive and putout the protrusion of the guide pin in the direction crossing the guidepin insertion hole.

According to still another aspect of the invention, there is provided amethod of assembling an optical fiber connector including a ferrule thathas a guide pin insertion hole into which a positioning guide pin of anopposite optical fiber connector can be inserted so as to be pulled outtherefrom, an optical fiber of which one end portion reaching a jointend face of the ferrule is fixed to the ferrule and of which the otherend portion extends from the ferrule, and a pin clamp that can beattached to a protrusion protruding from the opposite side to the jointend face of the ferrule in the guide pin inserted into the guide pininsertion hole so as to be detached therefrom in the direction crossingthe guide pin insertion hole, wherein the pin clamp includes a fittingrecessed portion that is fitted to the protruding portion of the guidepin to regulate the movement in the length direction of the guide pin,and the fitting recessed portion is formed to receive and put out theprotrusion of the guide pin in the direction crossing the guide pininsertion hole, the method including the steps of: splicing the otherend portion of the optical fiber to a front end portion of an externaloptical fiber; and attaching the pin clamp to the protrusion of theguide pin so that the protrusion of the guide pin is locked to thefitting recessed portion from the direction crossing the guide pininsertion hole.

According to still another aspect of the invention, there is provided acap-attached optical fiber connector including: an optical fiberconnector that is assembled (coupled) to a terminal of an opticaltransmission medium in which an optical fiber and a fiber-like tensilemember extending along the optical fiber are covered with a sheath; andan optical fiber connector cap that is detachably attached to a frontend portion which is an end portion of the optical fiber connector,wherein the optical fiber connector includes a ferrule, a housing havinga sleeve shape for receiving the ferrule and having a ring member fixingportion fixing a ring member on the outer circumference thereof, and aninserted optical fiber which is inserted into and fixed to the ferruleand of which a portion extending rearward from the ferrule is opticallyconnected to an optical fiber drawn out of the terminal of the opticaltransmission medium, wherein a tensile member detaining portiondetaining the tensile member of the optical transmission medium isprovided to the outer surface of the body of the optical fiber connectorcap, and wherein the tensile member can be fixed to the housing byfixing the ring member to the ring member fixing portion in a statewhere the tensile member extending forward through the vicinity of thering member fixing portion from the terminal of the optical transmissionmedium is detained in the tensile member detaining portion.

According to still another aspect of the invention, there is provide acap-attached optical fiber connector including: an optical fiberconnector that is assembled to a terminal of an optical transmissionmedium in which an optical fiber and a fiber-like tensile memberextending along the optical fiber are covered with a sheath; and anoptical fiber connector cap that is detachably attached to a front endportion which is an end portion of the optical fiber connector, whereinthe optical fiber connector includes a ferrule into and to which anoptical fiber drawn out of the terminal of the optical transmissionmedium is inserted and fixed and a housing having a sleeve shape forreceiving the ferrule and having a ring member fixing portion fixing aring member on the outer circumference thereof, wherein a tensile memberdetaining portion detaining the tensile member of the opticaltransmission medium is provided to the outer surface of the body of theoptical fiber connector cap, and wherein the tensile member can be fixedto the housing by fixing the ring member to the ring member fixingportion in a state where the tensile member extending forward throughthe vicinity of the ring member fixing portion from the terminal of theoptical transmission medium is detained in the tensile member detainingportion.

The ring member fixing portion may be a screw portion to which a screwedring member can be screwed, and the tensile member may be fixed to thehousing by screwing the screwed ring member to the screw portion in astate where the tensile member extending forward through the vicinity ofthe screw portion from the terminal of the optical transmission mediumis detained in the tensile member detaining portion.

The ring member fixing portion may be a swage ring attachment portion towhich a swage ring can be fixed by swaging, and the tensile member maybe fixed to the housing by fixing the swage ring to the swage ringattachment portion in a state where the tensile member extending forwardthrough the vicinity of the swage ring attachment portion from theterminal of the optical transmission medium is detained in the tensilemember detaining portion.

The tensile member detaining portion of the optical fiber connector capmay be a hooking protrusion protruding from the outer surface of thebody of the optical fiber connector cap and capable of hooking anddetaining the tensile member.

The ferrule may be a multi-core ferrule of a pin-fitting positioningtype which is positioned and butt-jointed by locking a pair of guidepins protruding from an end face of one of the ferrule and an oppositeferrule butt-jointed thereto to a pair of guide pin holes formed in theend face of the other and a plurality of the inserted optical fibers maybe inserted into and fixed to the ferrule.

According to still another aspect of the invention, there is provided amethod of assembling an optical fiber connector to a terminal of anoptical transmission medium in which an optical fiber and a fiber-liketensile member extending along the optical fiber are covered with asheath, including: a fiber connecting step of optically connecting theoptical fiber drawn out of the terminal of the optical transmissionmedium to a rear extension which is a portion extending backward from aferrule of an inserted optical fiber inserted into and fixed to theferrule; a housing assembling step of assembling a housing of theoptical fiber connector to the front side of the terminal of the opticaltransmission medium and receiving a spliced portion of the insertedoptical fiber and the optical fiber of the optical transmission mediumand the ferrule after the fiber connecting step; and a tensile memberfixing step of detaining a tensile member extending forward through thevicinity of a ring member fixing portion formed on the outercircumference of the housing from the terminal of the opticaltransmission medium in a tensile member detaining portion formed on theouter surface of a body of an optical fiber connector cap in a statewhere the optical fiber connector cap is detachably attached to a frontend portion of the housing and then fixing the tensile member to thehousing by fixing a ring member to the ring member fixing portion.

The ring member fixing portion may be a screw portion to which a screwedring member can be screwed, and the tensile member fixing step mayinclude fixing the tensile member to the housing by screwing the screwedring member to the screw portion in a state where the tensile memberextending forward through the vicinity of the screw portion from theterminal of the optical transmission medium is detained in the tensilemember detaining portion.

The ring member fixing portion may be a swage ring attachment portion towhich a swage ring can be fixed by swaging, and the tensile memberfixing step may include fixing the tensile member to the housing byfixing the swage ring to the swage ring attachment portion in a statewhere the tensile member extending forward through the vicinity of theswage ring attachment portion from the terminal of the opticaltransmission medium is detained in the tensile member detaining portion.

The tensile member detaining portion of the optical fiber connector capmay be a hooking protrusion protruding from the outer surface of thebody of the optical fiber connector cap and capable of hooking anddetaining the tensile member.

The fiber connecting step may include a fusion-splicing and reinforcingstep of fusion-splicing the inserted optical fiber and the optical fiberof the optical transmission medium to each other and then reinforcingthe fusion-spliced portion by the use of a reinforcing member.

The fusion-splicing and reinforcing step may include fusion-splicing theinserted optical fiber and the optical fiber of the optical transmissionmedium to each other, then pinching the fusion-spliced portion between apair of pinch members, which is used as the reinforcing member, eachhaving an adhesion layer which can be depressed at a position where theinserted optical fiber and the optical fiber of the optical transmissionmedium on the inner surface which comes in contact with a rear extensionof the inserted optical fiber and the optical fiber of the opticaltransmission medium, and closely adhering the adhesion layers to theouter circumferential surfaces of the optical fibers in thefusion-spliced portion.

The pair of pinch members may include pinching engagement portions thatpinch the fusion-spliced portion by engaging with each other and thatmaintain a pressing force for closely adhering the adhesion layers tothe outer circumferential surfaces in the fusion-spliced portion theinserted optical fiber and the optical fiber of the optical transmissionmedium.

The adhesion layers may be formed of rubber or elastomer.

The ferrule may be a multi-core ferrule of a pin-fitting positioningtype which is positioned and butt-jointed by locking a pair of guidepins protruding from an end face of one of the ferrule and an oppositeferrule butt-jointed thereto to a pair of guide pin holes formed in theend face of the other and a plurality of the inserted optical fibers areinserted into and fixed to the ferrule.

According to still another aspect of the invention, there is provided anoptical fiber connector cap which is detachably attached to an endportion of an optical fiber connector and in which a tensile memberdetaining portion that fixes a tensile member extending from a terminalof an optical transmission medium when assembling the optical fiberconnector to the terminal of the optical transmission medium in which anoptical fiber and a fiber-like tensile member extending along theoptical fiber are covered with a sheath is provided to the outer surfaceof the optical fiber connector cap.

The tensile member detaining portion may be a hooking protrusion capableof hooking and detaining the tensile member.

According to still another aspect of the invention, there is provided anoptical fiber connector assembling tool used to assemble an opticalfiber connector, the optical fiber connector including a ferrule, aninserted optical fiber of which one end portion is fixed to the ferruleand of which the other end portion protrudes from the ferrule, anexternal optical fiber of which a front end portion is fusion-spliced tothe other end portion of the inserted optical fiber, and a pair ofreinforcing members that pinches and reinforces the fusion-splicedportion of the other end portion of the inserted optical fiber and thefront end portion of the external optical fiber, the pair of reinforcingmembers including a first reinforcing member having a shaft portion atan end opposite to the ferrule and a second reinforcing member opposedto the first reinforcing member, the optical fiber connector assemblingtool including a bearing supporting portion which includes a reinforcingmember holding portion holding the second reinforcing member at apredetermined position and a bearing portion rotatably holding the shaftportion of the first reinforcing member, wherein the bearing supportingportion enables the first reinforcing member to rotationally move towardthe second reinforcing member held by the reinforcing member holdingportion until the first reinforcing members pinch the fusion-splicedportion.

The optical fiber connector assembling tool may further include: a coreholding portion that holds the external optical fiber; and a pressingcover that presses the external optical fiber on the core holdingportion.

The shaft portion may protrude to one side and the other side of thefirst reinforcing member, the bearing supporting portion may include apair of support members opposed to each other, and the bearing portionmay be formed in each of the pair of support members and supports theshaft portion protruding on one side and the other side of the firstreinforcing member.

According to still another aspect of the invention, there is provided anoptical fiber connector assembling set including the above-mentionedoptical fiber connector assembling tool and the optical fiber connector.

According to still another aspect of the invention, there is provided amethod of assembling an optical fiber connector using theabove-mentioned optical fiber connector assembling tool, including:before pinching the fusion-spliced portion between the pair ofreinforcing members, a step of holding the second reinforcing member onthe reinforcing member holding portion, a step of placing thefusion-spliced portion on the second reinforcing member, a step ofholding the shaft portion of the first reinforcing member on the bearingportion, and a step of rotating the first reinforcing member toward thesecond reinforcing member about the shaft portion in the bearing portionuntil the fusion-spliced portion is pinched between the firstreinforcing member and the second reinforcing member.

An optical fiber connector of the invention includes: a ferrule; aninserted optical fiber of which one end portion is fixed to the ferruleand an other end portion protrudes from the ferrule; an external opticalfiber of which a front end portion is fusion-spliced to the other endportion of the inserted optical fiber; and one or more reinforcingmembers that reinforce the fusion-spliced portion of the other endportion of the inserted optical fiber and the front end portion of theexternal optical fiber

It is preferable that the optical fiber connector of the inventionfurther include an adhesion layer applied on the inner surface of thereinforcing members. The adhesion layer covers an area where theinserted optical fiber and the external optical fiber come in contactwith each other, and adheres to the outer surfaces of the other endportion of the inserted optical fiber and the front end portion of theexternal optical fiber.

In the optical fiber connector of the invention, it is preferable thatthe adhesion layer include rubber or an elastomer.

In the optical fiber connector of the invention, it is preferable thatthe one or more reinforcing members include a pair of reinforcingmembers having protuberance portions and recessed portions engaging witheach other. The adhesion layer maintains the engaging of theprotuberance portions and the recessed portions with each other.

It is preferable that the optical fiber connector of the inventionfurther include a ferrule boot which covers the surrounding of the otherend portion of the inserted optical fiber. The ferrule boot is attachedto the ferrule. The one or more reinforcing members further secure theferrule boot to the ferrule.

A method of assembling an optical fiber connector of the invention,includes: fusion-splicing an other end portion of an inserted opticalfiber to a front end portion of an external optical fiber, one endportion of the inserted optical fiber being fixed to a ferrule and theother end portion being protruded from the ferrule; and applying one ormore reinforcing members to secure the fusion-spliced portion of theother end portion of the inserted optical fiber and the front endportion of the external optical fiber to the ferrule.

It is preferable that the method of assembling an optical fiberconnector of the invention further include applying an adhesion layer onthe inner surface of the reinforcing members. The adhesion layer coversan area where the inserted optical fiber and the external optical fibercome in contact with each other, and adheres to the outer surfaces ofthe other end portion of the inserted optical fiber and the front endportion of the external optical fiber.

In the method of assembling an optical fiber connector of the invention,it is preferable that the adhesion layer include rubber or an elastomer.

In the method of assembling an optical fiber connector of the invention,it is preferable that the one or more reinforcing members include a pairof reinforcing members having protuberance portions and recessedportions engaging with each other. The adhesion layer maintains theengaging of the protuberance portions and the recessed portions witheach other.

It is preferable that the method of assembling an optical fiberconnector of the invention further include applying a ferrule boot tocover the surrounding of the other end portion of the inserted opticalfiber, the ferrule boot being attached to the ferrule. The ferrule bootis secured to the ferrule by the one or more reinforcing members.

In the method of assembling an optical fiber connector of the invention,it is preferable that the one or more reinforcing members include afirst reinforcing member having a shaft portion and a second reinforcingmember. The securing of the fusion-spliced portion between the first andsecond reinforcing members is performed using an assembling toolincluding a reinforcing member holding portion and a bearing portion.The method includes: holding the second reinforcing member on thereinforcing member holding portion at a predetermined position, placingthe fusion-spliced portion on the second reinforcing member, holding theshaft portion of the first reinforcing member on the bearing portion,and rotating the first reinforcing member toward the second reinforcingmember about the shaft portion in the bearing portion until thefusion-spliced portion is pinched between the first reinforcing memberand the second reinforcing member.

It is preferable that the method of assembling an optical fiberconnector of the invention further include arranging the firstreinforcing member having the shaft portion at an end in the lengthdirection of the inserted optical fiber and the external optical fiber;arranging the second reinforcing member opposed to the first reinforcingmember as a pair of reinforcing members; and applying an adhesion layeron the inner surface of the pair of reinforcing members, covering anarea where the inserted optical fiber and the external optical fibercome in contact with each other, and adhering to the outer surfaces ofthe other end portion of the inserted optical fiber and the front endportion of the external optical fiber.

It is preferable that the method of assembling an optical fiberconnector of the invention further include interposing thefusion-spliced portion between the pair of reinforcing members to causethe adhesion layer to adhere to the outer circumferential surface of theinserted and external optical fibers in the fusion-spliced portion.

A pin clamp used of the invention for an optical fiber connectorincludes a ferrule that has a guide pin insertion hole being formed toreceive a positioning guide pin of an opposite optical fiber connectorand an optical fiber of which one end portion reaching a joint end faceof the ferrule is fixed to the ferrule and of which an other end portionextends from the ferrule. The pin clamp, which can be attached to aprotrusion protruding from the opposite side to the joint end face ofthe ferrule, is formed to secure the positioning guide pin in the guidepin insertion hole, and can be detached from the ferrule in thedirection crossing the guide pin insertion hole The pin clamp includes afitting recessed portion being formed to fit the protruding portion ofthe positioning guide pin to regulate the movement in the lengthdirection of the positioning guide pin. The fitting recessed portion isformed to receive the protrusion of the guide pin in the directioncrossing the guide pin insertion hole.

A method of assembling an optical fiber connector of the inventionincluding a ferrule that has a guide pin insertion hole being formed toreceive a positioning guide pin of an opposite optical fiber connector,an optical fiber of which one end portion reaching a joint end face ofthe ferrule is fixed to the ferrule and of which an other end portionextends from the ferrule, and a pin clamp that can be attached to aprotrusion protruding from the opposite side to the joint end face ofthe ferrule being formed to secure the guide pin in the guide pininsertion hole, and can be detached from the ferrule in the directioncrossing the guide pin insertion hole, the pin clamp includes a fittingrecessed portion being formed to fit the protruding portion of the guidepin to regulate the movement in the length direction of the guide pin,and the fitting recessed portion being formed to receive and put out theprotrusion of the guide pin in the direction crossing the guide pininsertion hole. The method includes the steps of: splicing the other endportion of the optical fiber to a front end portion of an externaloptical fiber; and attaching the pin clamp to the protrusion of theguide pin so that the protrusion of the guide pin is locked to thefitting recessed portion from the direction crossing the guide pininsertion hole.

An optical fiber connector of the invention includes: a ferrule that hasa guide pin insertion hole being formed to receive a positioning guidepin of an opposite optical fiber connector; an optical fiber of whichone end portion reaching a joint end face of the ferrule is fixed to theferrule and of which an other end portion extends from the ferrule; anda pin clamp that can be attached to a protrusion protruding from theopposite side to the joint end face of the ferrule being formed tosecure the positioning guide pin in the guide pin insertion hole, andcan be detached from the ferrule in the direction crossing the guide pininsertion hole. The pin clamp includes a fitting recessed portion isformed to fit the protruding portion of the positioning guide pin toregulate the movement in the length direction of the positioning guidepin. The fitting recessed portion is formed to receive the protrusion ofthe guide pin in the direction crossing the guide pin insertion hole.

In the optical fiber connector of the invention, it is preferable thatthe fitting recessed portion is formed to receive the protrusion of theguide pin that has a large-diameter portion and a small-diameter portionhaving a diameter smaller than that of the large-diameter portion at thetip thereof. The fitting recessed portion is locked to thesmall-diameter portion to regulate the movement of the large-diameterportion toward the tip.

In the optical fiber connector of the invention, it is preferable thatthe ferrule have two guide pin insertion holes including the guide pininsertion hole, and the two guide pin insertion holes be formed on bothsides with the optical fiber pinched there between, The pin clamp has abottom portion and side wall portions formed on both sides thereof and aspace surrounded with the bottom portion and the side wall portions onboth sides thereof serves as an insertion space of the optical fiber.The pin clamp has two fitting recessed portions, which are formed in theside wall portions on both sides.

An optical fiber connector cap of the invention which is detachablyattached to an end portion of an optical fiber connector and in which atensile member detaining portion that fixes a tensile member extendingfrom a terminal of an optical transmission medium when assembling theoptical fiber connector to the terminal of the optical transmissionmedium in which an optical fiber and a fiber-like tensile memberextending along the optical fiber are covered with a sheath is providedto the outer surface of the optical fiber connector cap.

In the optical fiber connector cap of the invention, it is preferablethat the tensile member detaining portion include a hooking protrusioncapable of hooking and detaining the tensile member.

An optical fiber connector assembling tool of the invention includes: abearing supporting portion which includes a reinforcing member holdingportion being formed to hold a second reinforcing member at apredetermined position, and a bearing portion being formed to rotatablyhold a shaft portion of a first reinforcing member. The bearing portionenables the first reinforcing member to rotationally move toward thesecond reinforcing member held by the reinforcing member holding portionuntil the first reinforcing member pinch the fusion-spliced portion. Theshaft portion of the first reinforcing member is positioned at an endopposite to a ferrule, and the second reinforcing member being opposedto the first reinforcing member. The ferrule is part of an optical fiberconnector having an inserted optical fiber of which one end portion isfixed to the ferrule and an other end portion protrudes from theferrule, and has an external optical fiber of which a front end portionis fusion-spliced to the other end portion of the inserted opticalfiber. The first and second reinforcing members pinch and reinforce thefusion-spliced portion of the other end portion of the inserted opticalfiber and the front end portion of the external optical fiber.

A method of assembling an optical fiber connector using theabove-described optical fiber connector assembling tool, includes:before pinching the fusion-spliced portion between the first and secondreinforcing members, holding the second reinforcing member on thereinforcing member holding portion, placing the fusion-spliced portionon the second reinforcing member, holding the shaft portion of the firstreinforcing member on the bearing portion, and rotating the firstreinforcing member toward the second reinforcing member about the shaftportion in the bearing portion until the fusion-spliced portion ispinched between the first reinforcing member and the second reinforcingmember.

Advantageous Effects of the Invention

According to the invention, after one end portion of an inserted opticalfiber of which the other end is fixed to the ferrule and an end portionof an external optical fiber are fusion-spliced to each other outsidethe ferrule, the fusion-spliced portion can be pinched and maintainedbetween a pair of reinforcing members and it is not necessary to passthe external optical fiber through the reinforcing members before thefusion splicing, thereby facilitating the work of fusion-splicing theoptical fibers and the work of reinforcing the fusion-spliced portion.Since the adhesion layers that are depressed by the contact with theoptical fibers to closely adhere to the outer circumferential surfacesare provided to the inner surface of the reinforcing members, it is notnecessary to provide a mechanism such as a V groove or a U groove foraligning the optical fibers to the inner surfaces of the reinforcingmembers.

According to the invention, since the pin clamp includes the fittingrecessed portion receiving and putting out the protrusion of the guidepin in the direction crossing the guide pin insertion hole, it ispossible to release the movement regulation in the length direction ofthe guide pin and to detach the guide pin, by moving the pin clamp inthe direction.

Accordingly, the shape (male form) having a guide pin and the shape(female form) not having a guide pin can be easily switched to eachother, thereby improving the workability on the splicing site.

Since it is not necessary to move the pin clamp backward when detachingthe guide pin, the spliced portion of the optical fibers is notadversely influenced. Accordingly, since it is not necessary toguarantee a space for movement of the pin clamp between the ferrule andthe spliced portion, it is possible to reduce the size of the opticalfiber connector in the length direction.

Since the pin clamp includes the fitting recessed portion to which theprotrusion of the guide pin is locked, it is possible to prevent theguide pin from falling out toward the front end.

According to the invention, in the work of assembling an optical fiberconnector to a terminal of an optical transmission medium, a tensilemember extending from the terminal of the optical transmission mediumcan be detained in the tensile member detaining portion of an opticalfiber connector cap attached to the housing of the optical fiberconnector. Accordingly, it is possible to simply achieve a state wheretension acts on the tensile member extending from the terminal of theoptical transmission medium, by only detaining the tensile memberextending from the terminal of the optical transmission medium in thetensile member detaining portion of the optical fiber connector capwithout using a tool for fixing an optical fiber connector, an opticalfiber cord, and a tensile member extending from a terminal of the cordas in the background art. As a result, it is possible to reduce thelabor for the work of assembling the optical fiber connector to theterminal of the optical transmission medium and to improve the workefficiency of the assembling work.

Since the optical fiber connector cap has a constitution simpler thanthat of the swaging tool in the background art and is available at acost lower than that of the swaging tool, it is possible to reduce thecost for assembling the optical fiber connector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a sectional view illustrating an optical fiber connectoraccording to a first embodiment of the invention and is a sectional viewtaken along a plane in which a multi-core optical fiber is arranged.

FIG. 1B is a sectional view illustrating the optical fiber connectorshown in FIG. 1A and is a sectional view taken along a planeperpendicular to the plane shown in FIG. 1A and parallel to the lengthdirection of the optical fiber.

FIG. 2A is a sectional view illustrating a ferrule and a slicereinforcing portion of the optical fiber connector shown in FIGS. 1A and1B and is a sectional view taken along the plane in which the multi-coreoptical fiber is arranged.

FIG. 2B is a sectional view illustrating the ferrule and the slicereinforcing portion of the optical fiber connector shown in FIGS. 1A and1B and is a sectional view taken along a plane perpendicular to theplane shown in FIG. 2A and parallel to the length direction of theoptical fiber.

FIG. 3 is a plan view illustrating an inserted optical fiber and anexternal optical fiber of the optical fiber connector shown in FIGS. 1Aand 1B.

FIG. 4A is a perspective view illustrating a first reinforcing member ofthe slice reinforcing portion shown in FIGS. 2A and 2B.

FIG. 4B is a perspective view illustrating a second reinforcing memberof the slice reinforcing portion shown in FIGS. 2A and 2B.

FIG. 5 is a side view illustrating a state where the first reinforcingmember and the second reinforcing member shown in FIGS. 4A and 4B areopposed to each other with a gap therebetween.

FIG. 6 is a side view illustrating a state where the first reinforcingmember and the second reinforcing member shown in FIGS. 4A and 4B arecombined.

FIG. 7 is a sectional view taken along line S-S of FIG. 6.

FIG. 8 is a schematic diagram illustrating an example of a state wherethe second reinforcing member is placed on an assembling tool.

FIG. 9 is a schematic diagram illustrating an example of a state where afusion-sliced portion is placed on the second reinforcing member.

FIG. 10 is a schematic diagram illustrating an example of a state wherea shaft portion of the first reinforcing member is held in a bearingportion of the assembling tool.

FIG. 11 is a schematic diagram illustrating an example of a state wherea pressing cover of the assembling tool is closed.

FIG. 12 is a schematic diagram illustrating an example of a state wherethe fusion-sliced portion is held between the first reinforcing memberand the second reinforcing member.

FIG. 13 is a schematic diagram illustrating an example of a state wherethe slice reinforcing portion is detached from the assembling tool.

FIG. 14 is a schematic diagram illustrating an example of a state wherethe fusion-sliced portion is held between the first reinforcing memberand the second reinforcing member using the assembling tool having apressing cover on both sides of the reinforcing members.

FIG. 15 is a schematic diagram illustrating an example of a state wherethe slice reinforcing portion assembled using the assembling tool havinga pressing cover on both sides of the reinforcing members is detachedfrom the assembling tool.

FIG. 16 is a sectional view illustrating a state where an optical fiberis held in the slice reinforcing portion.

FIG. 17A is a sectional view illustrating a modification of the opticalfiber connector according to the invention and is a sectional view takenalong the plane in which a multi-core optical fiber is arranged.

FIG. 17B is a sectional view illustrating a modification of the opticalfiber connector shown in FIG. 17A and is a sectional view taken along aplane perpendicular to the plane shown in FIG. 17A and parallel to thelength direction of the optical fiber.

FIG. 18 is a perspective view illustrating a ferrule and a pin clamp ofan optical fiber connector according to a second embodiment of theinvention.

FIG. 19 is a perspective view illustrating the pin clamp shown in FIG.18.

FIG. 20 is a plan view illustrating the pin clamp shown in FIG. 18.

FIG. 21 is a front view illustrating the pin clamp shown in FIG. 18.

FIG. 22 is a perspective view illustrating the guide pin shown in FIG.18.

FIG. 23A is a sectional view illustrating an optical fiber connector andis a sectional view taken along a plane in which a multi-core opticalfiber is arranged.

FIG. 23B is a sectional view illustrating the optical fiber connectorshown in FIG. 23A and is a sectional view taken along a planeperpendicular to the plane shown in FIG. 23A and parallel to the lengthdirection of the optical fiber.

FIG. 24A is a sectional view illustrating a ferrule and a slicereinforcing portion of the optical fiber connector shown in FIGS. 23Aand 23B and is a sectional view taken along the plane in which themulti-core optical fiber is arranged.

FIG. 24B is a sectional view illustrating the ferrule and the slicereinforcing portion of the optical fiber connector shown in FIGS. 23Aand 23B and is a sectional view taken along a plane perpendicular to theplane shown in FIG. 24A and parallel to the length direction of theoptical fiber.

FIG. 25 is a plan view illustrating an inserted optical fiber and anexternal optical fiber of the optical fiber connector.

FIG. 26 is a diagram illustrating a usage of a pin clamp.

FIG. 27 is a diagram illustrating a usage of the pin clamp.

FIG. 28 is a diagram illustrating a usage of the pin clamp.

FIG. 29 is a diagram illustrating another example of the pin clamp.

FIG. 30 is a front view illustrating the pin clamp shown in FIG. 29.

FIG. 31 is a sectional view illustrating an optical fiber connector anda cap-attached optical fiber connector according to a third embodimentof the invention.

FIG. 32A is a diagram illustrating a method of assembling the opticalfiber connector shown in FIG. 31.

FIG. 32B is a diagram illustrating the optical fiber connectorassembling method subsequent to FIG. 32A.

FIG. 33 is a perspective view illustrating an example of a structure ofan optical fiber cord applicable to the invention.

FIG. 34 is a diagram illustrating an example where a loop to be hookedto a hooking protrusion of an optical fiber connector cap is formed in atensile fiber bundle extending from the optical fiber cord shown in FIG.33.

FIG. 35 is a diagram illustrating a fiber connecting step in an opticalfiber connector assembling method according to the first embodiment.

FIG. 36 is a sectional perspective view illustrating the structure of anexample of a reinforcing sleeve which can be suitably used in the fiberconnecting step (fusion-slicing and reinforcing step) of the opticalfiber connector assembling method according to the first embodiment.

FIG. 37 is a diagram illustrating the fiber connecting step(fusion-slicing and reinforcing step) using the reinforcing sleeve shownin FIG. 36.

FIG. 38 is a sectional view illustrating an optical fiber connectorobtained by assembling a cap to the optical fiber connector shown inFIG. 31.

FIG. 39 is a sectional view illustrating the optical fiber connector andthe cap-attached optical fiber connector according to the firstembodiment of the invention.

FIG. 40A is a diagram illustrating an optical fiber connector assemblingmethod according to a fourth embodiment of the invention.

FIG. 40B is a diagram illustrating the optical fiber connectorassembling method subsequent to FIG. 40A.

FIG. 41 is a diagram illustrating a step of attaching a ferrule to a tipof an optical fiber extending from the terminal of an optical fiber cordin the optical fiber connector assembling method according to the fourthembodiment.

FIG. 42A is a sectional view illustrating an optical fiber connector anda cap-attached optical fiber connector according to a fifth embodimentof the invention and is a sectional view taken along a plane in which amulti-core optical fiber is arranged.

FIG. 42B is a sectional view illustrating the optical fiber connectorand the cap-attached optical fiber connector shown in FIG. 42A and is asectional view taken along a plane perpendicular to the plane shown inFIG. 23A and parallel to the length direction of the optical fiber.

FIG. 43A is a sectional view illustrating a part (a splice reinforcingportion and the vicinity thereof) of the optical fiber connector shownin FIGS. 42A and 42B and is a sectional view taken along the plane inwhich the multi-core optical fiber is arranged.

FIG. 43B is a sectional view illustrating the part (the splicereinforcing portion and the vicinity thereof) of the optical fiberconnector shown in FIGS. 42A and 42B and is a sectional view taken alonga plane perpendicular to the plane shown in FIG. 43A and parallel to thelength direction of the optical fiber.

FIG. 44 is a diagram illustrating the relationship between the other endportion of the inserted optical fiber and the front end portion of theexternal optical fiber in the splice reinforcing portion shown in FIGS.43A and 43B.

FIG. 45A is a perspective view illustrating the structure of areinforcing member (a pinch member) (a first reinforcing member) used toassemble the splice reinforcing portion shown in FIGS. 43A and 43B.

FIG. 45B is a perspective view illustrating a second reinforcing memberof the splice reinforcing portion shown in FIGS. 43A and 43B.

FIG. 46 is a diagram illustrating a method of incorporating the pair ofreinforcing members shown in FIGS. 45A and 45B.

FIG. 47 is a diagram illustrating a method of incorporating the pair ofreinforcing members shown in FIGS. 45A and 45B.

FIG. 48 is a sectional view illustrating the relationship betweenadhesion layers of the reinforcing members when the pair of reinforcingmembers shown in FIGS. 45A and 45B is integrated.

FIG. 49 is a sectional view illustrating a state where the pair ofreinforcing members shown in FIGS. 45A and 45B is integrated and afusion-spliced portion in which optical fibers are fusion-spliced ispinched therebetween.

FIG. 50 is a sectional view illustrating the work of incorporating apair of reinforcing members and pinching a fusion-spliced portion inwhich optical fibers are fusion-spliced therebetween in a step ofassembling the optical fiber connector shown in FIGS. 42A and 42B.

FIG. 51A is a perspective view illustrating the structure of an opticalfiber connector cap which can be attached to the front end portion ofthe optical fiber connector shown in FIGS. 42A and 42B.

FIG. 51B is a perspective view illustrating the structure of the opticalfiber connector cap which can be attached to the front end portion ofthe optical fiber connector shown in FIGS. 42A and 42B.

FIG. 51C is a perspective view illustrating the structure of the opticalfiber connector cap which can be attached to the front end portion ofthe optical fiber connector shown in FIGS. 42A and 42B.

FIG. 52 is a perspective view illustrating a tensile member fixing stepin the method of assembling the optical fiber connector shown in FIGS.42A and 42B.

FIG. 53A is a diagram illustrating another example of the tensile memberfixing step in the optical fiber connector assembling method accordingto the invention and is a diagram illustrating a constitution fixing atensile fiber to a swage ring attachment portion of the housing of theoptical fiber connector using a swage ring.

FIG. 53B is a diagram illustrating another example of the tensile memberfixing step subsequent to FIG. 53A.

FIG. 54 is a diagram illustrating another example of the optical fiberconnector cap according to the invention.

FIG. 55 is a perspective view illustrating an example of an assemblingtool.

FIG. 56 is a plan view of the assembling tool shown in FIG. 55.

FIG. 57 is a side view of the assembling tool shown in FIG. 55.

FIG. 58 is a longitudinal sectional view of the assembling tool shown inFIG. 55.

FIG. 59 is a partially-enlarged plan view of the assembling tool shownin FIG. 55.

FIG. 60 is a cross-sectional view of the assembling tool shown in FIG.55.

FIG. 61 is a diagram illustrating the flow of a method of assembling asplice reinforcing portion using the assembling tool shown in FIG. 55.

FIG. 62 is a diagram illustrating the flow subsequent to FIG. 61.

FIG. 63 is a diagram illustrating the flow subsequent to FIG. 62.

FIG. 64 is a diagram illustrating the flow subsequent to FIG. 63.

FIG. 65 is a diagram illustrating the flow of the method of assembling asplice reinforcing portion using the assembling tool shown in FIG. 55.

FIG. 66 is a diagram illustrating the flow subsequent to FIG. 65.

FIG. 67 is a diagram illustrating the flow subsequent to FIG. 66.

FIG. 68 is a diagram illustrating the flow subsequent to FIG. 67.

FIG. 69 is a perspective view illustrating a pressing jig pressing thefirst reinforcing member toward the second reinforcing member on theassembling tool shown in FIG. 55.

FIG. 70 is a perspective view illustrating the pressing jig shown inFIG. 69 as viewed from another direction.

FIG. 71 is a diagram illustrating a usage of the pressing jig shown inFIG. 69.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Hereinafter, the invention will be described on the basis of anexemplary embodiment with reference to the accompanying drawings.

FIGS. 1A and 1B show an optical fiber connector 10 according to a firstembodiment of the invention and FIGS. 2A and 2B show an important partof the optical fiber connector 10. The optical fiber connector 10receives a splice reinforcing portion 50, in which the other end portion43 of an inserted optical fiber 40 of which one end portion 42 is fixedto a ferrule 12 is fusion-spliced to a front end portion 46 of anexternal optical fiber 45 and the fusion-spliced portion 44 is pinchedbetween a pair of reinforcing members 51 and 54 to reinforce thefusion-spliced portion, in a housing or the like. FIGS. 1A and 1B may becomprehensively referred to as “FIG. 1”.

In the following description, in order to distinguish both sides in thelength direction (the lateral direction in FIG. 1) of an optical fiber,the side which a joint end face 14 of the ferrule 12 faces (the leftside in FIG. 1) may be referred to as “front” and the opposite side (theright side in FIG. 1) may be referred to as “rear”. FIGS. 2A and 2B maybe comprehensively referred to as “FIG. 2” and FIGS. 4A and 4B may becomprehensively referred to as “FIG. 4”.

An external optical fiber 45 is formed of an optical transmission mediumsuch as an optical fiber cord or an optical fiber cable having anoptical fiber. In this embodiment, the external optical fiber 45 is anoptical fiber cord including a multi-core optical fiber core 47including an optical fiber tape core in which a plurality optical fibers(optical fiber wires, which are not shown) are arranged in parallel inthe lateral direction perpendicular to the length direction thereof, atubular sheath 48 surrounding the multi-core optical fiber core 47, anda tensile fiber 49 received between the optical fiber core 47 and thesheath 48. In the front end portion 46 of the external optical fiber 45,the resin coating of the optical fiber core 47 and the resin coating ofthe optical fiber wires are removed and each of a plurality of bareoptical fibers (parts of core and clad) are separated.

Examples of the number of bare optical fibers 46 (the number of cores)included in the optical fiber core 47 include 2, 4, 8, and 12. In FIG.1A, the 12-core constitution is simplified and only 6 cores are shown.The optical fiber cord in this embodiment has a constitution in which asingle optical fiber tape core is received in a sheath, but is notparticularly to this constitution. For example, a constitution in whicha plurality of single-core optical fiber cores are received in a singlesheath, a constitution in which a plurality of optical fiber tape coresare received in a single sheath, and a constitution in which one or moreoptical fiber tape cores and signal-core optical fiber cores arereceived in a single sheath can be employed as the constitution of theexternal optical fiber.

Since an alignment mechanism such as a V groove is not necessary for apair of reinforcing members 51 and 54 to be described later, the numberof cores of the optical fiber which are held between a pair ofreinforcing members 51 and 54 is not specified depending on thestructure of a pair of reinforcing members 51 and 54, as long as it canbe received within the width range of adhesion layers 53 and 56. Thespecification of a pair of reinforcing members 51 and 54 applied tooptical fiber connectors with different numbers of cores such as 2cores, 4 cores, 8 cores, and 12 cores can be used in common. That is, bychanging only the ferrule to a ferrule having a suitable number ofcores, an optical fiber connector having a different number of cores canbe constructed, thereby contributing to a decrease in cost.

The sheath 48 is formed of a resin such as polyethylene and preferablyhas flexibility. A plurality of tensile fibers 49 extend along thelength direction of the optical fiber and functions as a tensile memberaccepting a tensile force (tension) to the optical transmission medium.The fiber material used for the tensile fiber 49 is not particularlylimited as long as it can provide a necessary tensile strength, andexamples thereof include aramid fiber, glass fiber, and carbon fiber.

The tensile member or the sheath is not essential to the invention. Forexample, an optical fiber core or an optical fiber tape core not havinga sheath may be used as the external optical fiber. In some structuresof an optical fiber cable or the like, metal wires such as steel wiresor various wires such as fiber-reinforced plastic (FRP) may be used asthe tensile member. Examples of the optical fiber cable include anoptical drop cable and an optical indoor cable.

The inserted optical fiber 40 is an optical fiber of which one endportion 42 is fixed to the ferrule 12 and of which the other end portion43 protrudes (extends) backward from the ferrule 12. In this embodiment,the inserted optical fiber 40 includes a multi-core optical fiber core41 which is an optical fiber tape core, and the resin coating of theoptical fiber core 41 and the resin coating of the optical fiber wiresare removed in one end portion 42 and the other end portion 43 of theoptical fiber core 41 so as to separate into a plurality of bare opticalfibers (parts of core and clad).

The optical fiber used as the inserted optical fiber 40 is not limitedto the multi-core optical fiber, but a structure in which one or moreshort single-core optical fibers are inserted into a single ferrule, astructure in which one or more optical fiber tape cores and single-coreoptical fiber cores are received in a single ferrule, or the like may beemployed.

As shown in FIG. 3, the other end portion 43 of the inserted opticalfiber 40 and the front end portion 46 of the external optical fiber 45correspond to each other in a one-to-one manner and are fusion-splicedto each other. As shown in FIG. 2, the fusion-spliced portion 44 of theother end portion 43 of the inserted optical fiber 40 and the front endportion 46 of the external optical fiber 45 is pinched between a pair ofreinforcing members 51 and 54 to reinforce the fusion-spliced portion.The ferrule 12 around the inserted optical fiber 40 is not shown in FIG.3, but one end portion 42 of the inserted optical fiber 40 is preferablyfixed into an optical fiber insertion hole 13 of the ferrule 12 beforethe fusion-splice to the external optical fiber 45.

As shown in FIG. 2, the ferrule 12 includes a front end face (joint endface) 14 butt-jointed to a ferrule (not shown) of another optical fiberconnector, a rear end face 16 which is the opposite end face of thejoint end face 14, optical fiber insertion holes (micro holes) 13 openedin the joint end face 14, and a boot-receiving hole 17 opened in therear end face 16. The ferrule 12 can be formed, for example, as anintegrated molded product formed of plastic. The joint end face 14 ofthe ferrule 12 may be a vertical face perpendicular to the central axis(substantially matched with the optical axis of the optical fiber 42) ofthe optical fiber insertion holes 13, or may be an inclined faceinclined in a predetermined direction corresponding to a ferrule ofanother optical fiber connector.

The optical fiber insertion holes 13 are formed in the same number asthe number of optical fibers in one end portion 42 of the insertedoptical fiber 40. For example, a method of injecting an adhesive intothe optical fiber insertion holes 13 to adhere to the bare opticalfibers can be simply used as the method of fixing the bare opticalfibers which are one end portion 42 of the inserted optical fiber 40 tothe ferrule 12. The optical fiber insertion holes 13 are connected tothe boot-receiving hole 17. A ferrule boot 18 is attached around theoptical fiber core 41 and is received in the boot-receiving hole 17. Theferrule boot 18 is preferably formed of a flexible material such asrubber or elastomer, but the ferrule boot 18 may be formed of a materialsuch as a resin or a metal having low flexibility.

Examples of the number of optical fiber insertion holes 13 (the numberof cores) formed in the ferrule 12 include 2, 4, 8, and 12. In FIG. 1A,the structure of 12 cores is simplified and only 6 cores are shown. Inthe optical fiber connector 10 according to this embodiment, asingle-core ferrule may be used as the ferrule 12.

The optical fiber insertion holes 13 on the joint end face 14 of themulti-core ferrule 12 are arranged in a line to match with thearrangement of optical fibers pinched between the reinforcing members 51and 54 to be described later. The invention is not limited to theconstitution in which the arrangement of optical fibers in the ferrule12 are set to be the same as the arrangement of optical fibers in thesplice reinforcing portion 50, but the arrangement of optical fibersseparated for each core between the ferrule 12 and the splicereinforcing portion 50 may be changed.

For the purpose of alignment when coupling the ferrule 12 to anotherferrule of another optical fiber connector, a guide pin 15 passingthrough the joint end face 14 and the rear end face 16 may be provided.The tip of the guide pin 15 protrudes from the joint end face 14 and theguide pin is inserted into a guide pin insertion hole (not shown) formedin the ferrule of another optical fiber connector to suppress theshaking in the direction along the joint end face 14 (such as thevertical direction in FIG. 2A, the vertical direction in FIG. 2B, or aninclined direction obtained by combining the directions). When a guidepin is provided to a ferrule of another optical fiber connector, a guidepine insertion hole is provided to the ferrule 12. A hole 15 a formed asa trace of pulling out the guide pin 15 from the ferrule 12 may be usedas the guide pin insertion hole 15 a. Alternatively, the ferrule 12having a guide pin insertion hole formed thereon instead of the guidepin 15 may be used at the first time.

Preferably, the guide pin 15 can be attached and detached by theinsertion and the pulling-out into and from the guide pin insertion hole15 a, since it can be easily determined on the splicing site with whichof the optical fiber connector 10 and another optical fiber connector toprovide the guide pin. For example, when the jointed state of theoptical fiber connector 10 and another optical fiber connector isreleased, a pin clamp 19 is disposed on the rear end face 16 of theferrule 12 so as to prevent the guide pin 15 from being unintentionallypulled out. In this embodiment shown in FIG. 1, the pin clamp 19 fills agap between the ferrule 12 and the splice reinforcing portion 50 andincludes a spring seat 20 for accepting an impelling force (pressingforce based on elasticity) from a ferrule spring 24. Accordingly, evenwhen the guide pin 15 is not installed in the ferrule 12, the pin clamp19 is attached to the ferrule 12. The pin clamp 19 can be inserted intoand fixed to the ferrule 12 by, for example, irregularity or the like(not shown).

The guide pin 15 may be fixed to the guide pin insertion hole 15 a (forexample, by adhesion or embedment through insert molding) for use.

An example of the reinforcing members 51 and 54 used in this embodimentis shown in FIGS. 4 to 7. The first reinforcing member 51 used in theupper side of FIG. 2B is shown in FIG. 4A and the second reinforcingmember 54 used in the lower side of FIG. 2B is shown in FIG. 4B. In thisembodiment, the reinforcing members 51 and 54 includes reinforcingmember bodies 52 and 55 formed of a hard material such as a resin or ametal and adhesion layers 53 and 56 disposed on the inner surfacescoming in contact with the other end portion 43 of the inserted opticalfiber 40 and the front end portion 46 of the external optical fiber 45,respectively.

As shown in FIG. 16, the adhesion layers 53 and 56 are depressed at theposition where the inserted optical fiber and the external optical fiber(which are comprehensively represented by the optical fibers F in FIG.16) come in contact with each other to closely adhere to the outercircumferential surfaces of the optical fibers F in the vicinity of thefusion-spliced portion 44. Accordingly, a mechanism such as a V grooveor a U groove used to align the optical fibers is not necessary to formin the inner surfaces of the reinforcing members. In this embodiment,since the other end portion 43 of the inserted optical fiber 40 and thefront end portion 46 of the external optical fiber 45 are fusion-splicedin advance, the splice loss is small and the loss is not increased dueto the axial misalignment (misalignment of the optical axes) of bothoptical fibers or the separation of the end faces.

In the case of the groove-like mechanism such as a V groove or a Ugroove, when the outer diameter in the vicinity of the fusion-splicedportion 44 is greater than the original outer diameter of the opticalfibers (before the fusion splice), an excessive pressing force acts onthe fusion-spliced portion 44, thereby shortening the lifetime. On theother hand, when the outer diameter in the vicinity of thefusion-spliced portion 44 is smaller, the positioning of the opticalfibers is not stabilized and the positions of the optical fibers may bemisaligned in the lateral direction in the grooved mechanism. On thecontrary, when the adhesion layers 53 and 56 have deformabilityfollowing the outer circumferential surface of the optical fibers F, thepositioning of the optical fibers F is stabilized, thereby suppressingthe warp of the optical fibers F with the lapse of time or the increasein loss.

In this embodiment, as shown in FIG. 16, at the position where theoptical fibers F in the fusion-spliced portion 44 are pinched between apair of reinforcing members 51 and 54, the adhesion layers 53 and 56 ofthe pair of reinforcing members 51 and 54 closely adhere to each otheron both sides (on both sides in the width direction perpendicular to thelength direction) of the optical fibers F. Accordingly, it is possibleto suppress the warp of the optical fibers F with the lapse of time orthe increase in loss. Since there is no gap between the opposed adhesionlayers 53 and 56, it is possible to prevent the permeation of moistureor the like which may adversely influence the lifetime of bare opticalfibers (particularly, in the case of quartz optical fibers). When anopaque material is used for the adhesion layers 53 and 56, it ispossible to prevent the leakage of light (leaking light) from the gapbetween the adhesion layers 53 and 56.

The adhesion layers 53 and 56 are preferably formed of a flexibleelastic material such as rubber or elastomer. Accordingly, when theoptical fibers F are pinched between the adhesion layers 53 and 56 witha pressing force, the adhesion layers are depressed at the positionwhere they come in contact with the optical fibers F and thus moreclosely adhere to the outer circumferential surfaces of the opticalfibers F with the elastic force of the adhesion layers 53 and 56. Theelastic force of the adhesion layers 53 and 56 has such a magnitude thatthe original flat surface is restored, when the pressing force isreleased after the depression.

When a foamed material is used for the adhesion layers 53 and 56, it ispreferable that bubbles be small and the bubbles be independent of eachother (the bubbles be not connected). An adhesive (pressure-sensitiveadhesive) may be used as the adhesion layers 53 and 56, but it ispreferable that the adhesion layers 53 and 56 be non-adhesive (theadhesive force is small or zero to such an extent that the bare opticalfibers 43 and 46 can be easily detached after the temporary disposing)so as to dispose the bare optical fibers 43 and 46 again aftertemporarily disposing them. When the adhesive force of the surfaces ofthe adhesion layers 53 and 56 is weak, it is difficult to cause theadhesion layers 53 and 56 to closely adhere to the bare optical fibers43 and 46. Accordingly, it is preferable that the positionalrelationship between the first reinforcing member 51 and the secondreinforcing member 54 be fixed to maintain appropriate pressing forcesfrom both sides.

As shown in FIGS. 4 to 6, a pair of reinforcing members 51 and 54includes protuberance portions 61 and recessed portions 62,respectively, engaging with each other on both sides in the widthdirection (the direction perpendicular to the paper surface of FIGS. 5and 6) which is the direction perpendicular to the length direction ofthe inserted optical fiber 40 and the external optical fiber 45. Bycausing the protuberance portions (engaging protuberance portions) 61and the recessed portions (engaging recessed portions) 62 to engage witheach other, the state where the adhesion layers 53 and 56 of the pair ofreinforcing members 51 and 54 closely adhere to each other ismaintained. Accordingly, even when the adhesion therebetween is notmaintained with only the adhesive force between the adhesion layers 53and 56, it is possible to cause the adhesion layers 53 and 56 tosatisfactorily closely adhere to each other and thus to prevent thefirst reinforcing member 51 and the second reinforcing member 54 frombeing separated from each other.

In this embodiment, as shown in FIG. 4B, the body 55 of the secondreinforcing member 54 includes a bottom portion 57 and side wallportions 58 and 58 formed on both sides in the width direction thereofand the engaging recessed portion 62 is a through-hole formed in theside wall portions 58. Accordingly, it is possible to easily confirm theengagement state of the engaging recessed portions 61 from the outsidewith the naked eye or a magnifier. From the viewpoint of theincorporation of the reinforcing members 51 and 54, only the innersurfaces of the side wall portions 58 to form holes (blind holes) notpenetrating the outer surface as the engaging recessed portions. Insteadof forming the engaging protuberance portions in the first reinforcingmember and forming the engaging recessed portions in the secondreinforcing member 54, the engaging protuberance portions may be formedin the second reinforcing member and the engaging recessed portions maybe formed in the first reinforcing member 54. Various combinations suchas a combination of alternately forming the engaging protuberanceportion and the engaging recessed portion in the first reinforcingmember and alternately forming the engaging recessed portion and theengaging protuberance portion in the second reinforcing member so as tobe complementary thereto may be employed.

The side wall portion 58 of the second reinforcing member 54 is dividedinto a plurality of parts (tongue-shaped parts) by cutouts 59 and one ormore engaging recessed portions 62 are disposed on one side.Accordingly, as shown in FIG. 7, when the first reinforcing member 51 isinterposed between the pair of side wall portions 58 opposed to eachother in the width direction, the side wall portions 58 having theengaging recessed portions 62 can be independently opened and closed.Even when a set of engaging portions is loosened, the other engagingportions are not loosened therewith. In the front end portions (theupside in FIG. 7) of the side wall portions 58 protruding from thebottom wall portion 57, an inclined surface 58 a is formed on the innersurface side of the side wall portions 58. Accordingly, it is possibleto easily interpose the first reinforcing member 51 between the pair ofside walls 58 opposed to each other in the width direction. When theengaging protuberance portions 61 and the engaging recessed portions 62are disengaged from each other after the pair of reinforcing members 51and 54 are combined, a tool may be inserted into the clearance betweenthe inclined surface 58 a of the side wall portion 58 and the firstreinforcing member body 52 to easily push and open the side wall portion58 to the outside in the width direction.

The adhesion layers 53 and 56 in this embodiment include swelledportions 53 a and 56 a of which the surface is raised higher in thevicinity of the fusion-spliced portion 44 and thus the pressing forcecan be kept higher between the swelled portions 53 a and 56 a.Alleviated portions 53 b and 56 b which are lower in height than theswelled portions 53 a and 56 a and which are alleviated in pressingforce are disposed on both sides of the swelled portions 53 a and 56 a(on both sides in the length direction of the bare optical fibers 43 and46). Examples of a method of forming the swelled portions 53 a and 56 ainclude a method of forming protrusions in the reinforcing member bodies52 and 55 in the back of the adhesion layers 53 and 56 and a method ofpartially increasing the thicknesses of the adhesion layers 53 and 56.

The sets of engaging portions including the sets of the engagingprotuberance portions 61 and the engaging recessed portions 62 aredisposed in the length direction of the optical fibers. Specifically,one set (or two or more sets) is disposed at the position of the swelledportions 53 a and 56 a, one set (or two or more sets) is disposed at theposition of the alleviated portions 53 b and 56 b on the side of theinserted optical fiber 40, and one set (or two or more sets) is disposedat the position of the alleviated portions 53 b and 56 b on the side ofthe external optical fiber 45. Accordingly, the pressing force appliedto the fusion-spliced portion 44 from the swelled portions 53 a and 56 acan be adjusted by adjusting the positional relationship of the engagingportions in the swelled portions 53 a and 56 a. Even when the pressingforce of the swelled portions 53 a and 56 a is excessively strong andthe engaging portions are loosened due to the repulsive force betweenthe swelled portions 53 a and 56 a, the engaging portions in thealleviated portions 53 b and 56 b are not loosened well, therebypreventing the first reinforcing member 51 and the second reinforcingmember 54 from being separated from each other.

As shown in FIG. 2B, a ferrule boot 18 covering the part of the insertedoptical fiber 40 extending from the ferrule 12 is attached to theferrule 12. The pair of reinforcing members 51 and 54 (specifically, thebodies 52 and 55 thereof) include protrusions serving as boot clampingportions 52 a and 55 a at ends close to the ferrule 12 and the ferruleboot 18 is clamped between the boot clamping portions 52 a and 55 a.Accordingly, both ends of the ferrule boot 18 is tightly held betweenthe ferrule 12 and the pair of reinforcing members 51 and 54, therebysatisfactorily preventing the warp or damage of the inserted opticalfiber 40.

The method of assembling the optical fiber connector 10 according tothis embodiment includes a step of fusion-splicing the other end portion43 of the inserted optical fiber 40, of which one end portion 42 isfixed to the ferrule 12 and of which the other end portion 43 protrudesfrom the ferrule 12, to the front end portion 46 of the external opticalfiber 45 and then pinching the fusion-spliced portion 44 between thepair of reinforcing members 51 and 54 to integrate them into a body.Accordingly, the adhesion layers 53 and 56 disposed on the innersurfaces of the reinforcing members 51 and 54 can be caused to closelyadhere to the outer circumferential surfaces of the bare optical fibers43 and 46 in the fusion-spliced portion 44.

The reinforcing members 51 and 54 in this embodiment include a firstreinforcing member 51 having a shaft portion 60 at an end opposite tothe ferrule 12 and a second reinforcing member 54 opposed to the firstreinforcing member 51. A suitable assembling method in this case will bedescribed below with reference to FIGS. 8 to 13. In FIGS. 12 and 13, thebare optical fibers 43 and 46 are shown to be visible so as to easilysee the positions of the bare optical fibers 43 and 46 between theadhesion layers 53 and 56. However, it is preferable that the bareoptical fibers 43 and 46 be sealed between the adhesion layers 53 and 56after closing the reinforcing members 51 and 54, as shown in FIG. 16.

First, as shown on the upper side of FIG. 8, a structure in which theother end portion 43 of the inserted optical fiber 40 protruding fromthe ferrule 12 is fusion-spliced to the front end portion 46 of theexternal optical fiber 45 is prepared. In this embodiment, a ferrule towhich the guide pin 15, the ferrule boot 18, the pin clamp 19, and theinternal optical fiber 40 are attached in advance is used as the ferrule12 and the other end portion 43 of the inserted optical fiber 40 hasonly to be fusion spliced to the front end portion 46 of the externaloptical fiber 45 on the splicing site. When the pin clamp 19 can beattached and detached after assembling the splice reinforcing portion50, the steps shown in FIGS. 8 to 13 may be performed in a state wherethe guide pin 15 or the pin clamp 19 is detached from the ferrule 12.

As shown on the lower side of FIG. 8, the second reinforcing member 54is held on the assembling tool 70. The assembling tool 70 includes areinforcing member holding portion 71 holding the second reinforcingmember 54 at a predetermined position, a core holding portion 72 holdinga part of the optical fiber core 47 of the external optical fiber 45, anarm portion 73 (see FIG. 10) having a bearing portion 74 rotatablyholding the shaft portion 60 of the first reinforcing member 51, and apressing cover 75 (see FIG. 11) pressing the part of the optical fibercore 47 of the external optical fiber 45 against the core holdingportion 72.

The reinforcing member holding portion 71 preferably has a groovedstructure to holding the second reinforcing member 54 from both sides inthe width direction (the lateral direction in FIG. 7) of the bottom wallportion 57 so as for the second reinforcing member 54 not to move in thewidth direction. In this embodiment, the side wall portions 58 protrudeupward from the bottom wall portion 57. Accordingly, when the firstreinforcing member 51 is pushed between both side wall portions 58, bothside wall portions 58 may be opened until the protuberance portions 61of the first reinforcing member 51 reach the engaging recessed portions62 from the upside.

As shown in FIG. 9, the fusion-spliced portion 44 of the bare opticalfibers 43 and 46 is placed on the second reinforcing member 54. Theadhesion layer 56 formed on the inner surface of the second reinforcingmember 54 faces the upside and the fusion-spliced portion 44 is placedon the swelled portion 56 a of the adhesion layer 56. Since the bareoptical fibers 43 and 46 are thin (generally in the diameter range ofabout 60 to about 150 μm, for example, 125 μm more or less) and is notdesirable to directly touch with a hand, it is preferable that a holdernot shown be provided under the ferrule 12 and a thick part of theholder and the external optical fiber 45 be picked up for work.

As shown in FIG. 10, the shaft portion 60 of the first reinforcingmember 51 is held in the bearing portion 74.

At this time, the adhesion layer 53 formed on the inner surface of thefirst reinforcing member 51 is disposed to face the second reinforcingmember 54.

As shown in FIG. 11, the pressing cover 75 is closed from the upside ofthe optical fiber core 47 of the external optical fiber 45 to pinch theoptical fiber core 47 between the core holding portion 72 and thepressing cover 75. Before closing the pressing cover 75, the externaloptical fiber 45 is preferably attracted in the direction (to the rightside in FIG. 11) in which it goes apart from the ferrule 12 with a handto remove the loosening of the bare optical fibers 43 and 46 or theoptical fiber cores 41 and 47 before and after. When attracting theexternal optical fiber 45, the end portion (specifically, the bootclamping portion 55 a) of the second reinforcing member 54 on the sideof the ferrule 12 comes in contact with the rear end of the ferrule 12(specifically, the pin clamp 19) and the movement to the side of theinserted optical fiber 40 is stopped, whereby it is not necessary toparticularly press the ferrule 12 with a hand or the like.

In the above-mentioned steps, the time of performing the step of holdingthe shaft portion 60 of the first reinforcing member 51 in the bearingportion 74 is not particularly limited as long as it is before thefusion-spliced portion 44 is pinched between the pair of reinforcingmembers 51 and 54. For example, the step may be performed after thepressing cover 75 is closed. By providing the pressing cover 75, thestate where tension is applied to the optical fiber 45 can be maintainedwithout pressing the optical fiber, thereby improving the workability.Examples of the method of opening and closing the pressing cover 75include methods using a magnet, a screw, a spring, or the like inaddition to a method using a latch having an engaging claw orprotrusion.

In this embodiment, the optical fiber core 47 is pinched between thecore holding portion 72 and the pressing cover 75, but a part of theoptical fiber cord or the optical fiber cable may be pinchedtherebetween.

As shown in FIG. 12, the first reinforcing member 51 is rotationallymoved to the second reinforcing member 54 about the shaft portion 60 inthe bearing portion 74 to pinch the fusion-spliced portion 44 betweenthe pair of reinforcing members 51 and 54. Accordingly, the splicereinforcing portion 50 can be assembled to the rear side of the ferrule12 and the bare optical fibers 43 and 46 are sealed between the adhesionlayers 53 and 56.

When pinching the fusion-spliced portion 44 between the pair ofreinforcing members 51 and 54, the engaging protuberance portions 61 aremade to engage with the engaging recessed portions 62, as shown in FIG.16. The ferrule boot 18 is clamped between t boot clamping portions 52 aand 55 a formed at the ends of the pair of reinforcing members 51 and 54on the side of the ferrule 12.

Then, as shown in FIG. 13, the structure (see FIG. 2 for the sectionalstructure) in which the splice reinforcing portion 50 is assembled tothe rear side of the ferrule 12 is detached from the assembling tool 70.Since the bearing portion 74 has a U shape in which the bottom is asemicircular shape and the top is horizontally opened, the shaft portion60 can be easily detached from the bearing portion 74 by raising thesplice reinforcing portion 50 with a hand or the like.

In this way, by using the first reinforcing member 51 having the shaftportion 60 of which the central axis line is perpendicular to the lengthdirection of the optical fibers and the assembling tool 70 having thebearing portion 74, the first reinforcing member 51 falls out in thedirection parallel to the length direction of the optical fibers withrespect to the second reinforcing member 54 and it is thus possible tosuppress a rotational (twisting) force about the axis of the opticalfibers when the first reinforcing member 51 comes in contact with theoptical fibers.

Since the positional relationship between the reinforcing member holdingportion 71 and the bearing portion 74 are appropriately determined inadvance, the bearing portion 74 supporting the shaft portion 60 can beused as a reference for positioning the first reinforcing member 51 withrespect to the second reinforcing member 54. That is, since the secondreinforcing member 54 is not erroneously moved when attaching the shaftportion 60 to the bearing portion 74, the work is facilitated even withthe small size of the reinforcing members 51 and 54.

By assembling the housing receiving the ferrule 12 and the splicereinforcing portion 50 after assembling the splice reinforcing portion50 to the rear side of the ferrule 12, the optical fiber connector 10shown in FIG. 1 can be completed.

The optical fiber connector 10 described in this embodiment is amulti-core optical fiber connector and the example shown in the drawingsis an MPO type optical fiber connector (F13 type multi-core opticalfiber connector defined in the JIS C5982, MPO: Multi-fiber Push On). Theoptical fiber connector applicable to the invention is not limited tothe single-core type or the multi-core type.

The housing of the optical fiber connector 10 includes a sleeve-like(tubular) plug frame 21 and a sleeve-like (tubular) stop ring 30attached to the rear end of the plug frame 21. The side surface of theferrule 12 is held from the surrounding by the front opening 22 of theplug frame 21. An engaging claw 33 which can engage with an engagingwindow 27 formed in the side wall portion of the plug frame 21 is formedin the outer surface of the stop ring 30 so as to integrate the plugframe 21 and the stop ring 30 into a body. The ferrule spring 24 isdisposed around the splice reinforcing portion 50, the front end of thespring 24 is brought into contact with the spring seat 20 at the rearend of the pin clamp 19, and the rear end of the spring 24 is broughtinto contact with the spring seat 31 at the front end of the stop ring30.

When the joint end face 14 of the ferrule 12 is jointed to a ferrule ofanother optical fiber connector, the ferrule 12 is guided in the opening22 and pushed backward to contract the ferrule spring 24, an appropriateforce acts between the joint end face 14 of the ferrule 12 and a jointend face of a ferrule of another optical fiber connector, therebybringing the joint end faces into close contact with each other. Whenthe joint between the ferrule 12 and the ferrule of another opticalfiber connector is released, the ferrule spring 24 is stretched and theferrule 12 moves in the opening 22 and is restored to the originalposition.

An engaging portion 23 used for the MPO type connector plug to engagewith an engaging claw (not shown) of an MPO type connector adaptor or areceptacle is disposed on both sides (both side in the verticaldirection in FIG. 1A) in the width direction of the plug frame 21. Acoupling 25 is disposed on the outer circumference of the plug frame 21,and a pair of coupling springs 26 and 26 is received between the outercircumferential surface of the plug frame 21 and the innercircumferential surface of the coupling 25. Accordingly, the coupling 25can move forward and backward relative to the plug frame 21 with thestretching and contracting of the coupling springs 26 and 26. Theengaging portion 23 or the coupling 25 has the same constitution asdefined in the JIS or the like as the MPO type connector plug.

When the invention is applied to different types of optical fiberconnectors, the constituents required for the joint (connector joint) ofthe optical fiber connectors are installed in the ferrule or thehousing.

In the optical fiber connector 10 shown in FIG. 1, a cap 11 is providedto protect the front end portion of the ferrule 12 of the optical fiberconnector plug or the like. The cap 11 is detached in use (at the timeof jointing to another optical fiber connector). A key groove 11 alocked to a key 21 a formed on one of the side surfaces of the plugframe 21 is formed in the inner surface of the cap 11. The key 21 a ofthe plug frame 21 is conventionally installed to prevent thevertically-reverse use (of the top and bottom in FIG. 1B) of an opticalfiber connector plug, and the key groove 11 a of the cap 11 is installedon both sides in the vertical direction. Accordingly, it is possible toattach the cap 11 to the optical fiber connector 10 withoutdistinguishing the upside and downside of the cap 11.

A through-hole 32 passing in the front-rear direction (the lateraldirection in FIG. 1) along the length direction of the optical fiber isformed in the stop ring 30. The cross-sectional shape (the sectionalshape in the plane perpendicular to the length direction of the opticalfiber) of the through-hole 32 has at least a size which can receive theshape of the cross-sectional shape of the splice reinforcing portion 50.Accordingly, when the stop ring 30 is pushed in toward the plug frame 21from the rear side of the splice reinforcing portion 50 in a state wherethe ferrule 12 is inserted into the opening 22 of the plug frame 21, thestop ring 30 is prevented from interfering with the splice reinforcingportion 50 (hindering the push thereof). When the stop ring 30 is pushedin toward the plug frame 21 from the rear side of the splice reinforcingportion 50, the engaging claw 33 is drawn into the splice reinforcingportion 50 just before the engaging claw 33 reaches the engaging window27. Accordingly, on the back surface side of the engaging claw 33, agroove 32 a is formed in the inner surface of the through-hole 32,thereby avoiding the interference of the splice reinforcing portion 50with the back surface of the engaging claw 33.

An external screw 34 is formed on the outer circumferential surface ofthe rear end portion of the stop ring 30. An internal screw 36 formed onthe inner circumferential surface of the screw ring 35 can be fastenedto the external screw 34. The front end portion of the tensile fiber 49of the external optical fiber 45 can be pinched and fixed between theexternal screw 34 and the internal screw 36. The screw ring 35 includesan opening 37 at the rear end thereof, and a part of the tensile fiber49 of the external optical fiber 45 and the optical fiber core 47 isinserted into the opening 37. The cross-sectional shape (the sectionalshape in the plane perpendicular to the length direction of the opticalfiber) of the opening 37 preferably has a certain opening size so as toavoid the contact of the tensile fiber 49 with the splice reinforcingportion 50.

A boot 65 for an external optical fiber for protecting the externaloptical fiber 45 is attached to the outer circumferential surface of thescrew ring 35. The boot 65 is generally formed of a flexible materialsuch as rubber or elastomer. In this embodiment, a protective tube 66 isattached around the sheath 48 of the external optical fiber 45 and anannular locking portion 67 having a large diameter at the front endportion of the tube 66 is inserted into the boot 65.

The sequence of assembling the housing or the like is not particularlylimited, but the following sequence can be employed as an example.

As an advance preparation before the fusion splice, the ferrule spring24, the stop ring 30, the screw ring 35, the external optical fiber boot65, and the protective tube 66 are made to pass around the externaloptical fiber 45. These components are preferably arranged on the rearside (the right side in FIG. 1) so as not to interfere with the fusionsplice.

As described above, the bare optical fibers 43 and 46 arefusion-spliced, the splice reinforcing portion 50 is assembled thereto(see FIGS. 8 to 13), the plug frame 21 is attached thereto from thefront side (the left side in FIG. 1) of the ferrule 12 to dispose theferrule 12 in the opening 22 of the plug frame 21, the stop ring 30 ispushed into the plug frame 21 to cause the engaging claw 33 to engagewith the engaging window 27, and the ferrule spring 24 is received alongwith the ferrule 12 and the splice reinforcing portion 50. The cap 11and the coupling 25 may be attached to the plug frame 21 in advance ormay be attached thereto after the cap 11 and the coupling 25 areattached to the stop ring 30.

The front end portion of the tensile fiber 49 is placed on the externalscrew 34 of the stop ring 30 and the internal screw 36 of the screw ring35 is fastened to the external screw 34 to fix the front end portion ofthe tensile fiber 49. When the front end portion of the tensile fiber 49extends over the outer circumference of the plug frame 21, the tensilefiber is cut out if necessary. The boot 65 is attached to the stop ring30. The optical fiber connector 10 shown in FIG. 1 can be assembledthrough this sequence.

When the external optical fiber does not include a tensile fiber, theinternal screw 36 of the screw ring 35 is fastened to the external screw34 of the stop ring 30 to integrate the housing into a body, withoutpinching the tensile fiber.

(Method of Reinforcing Fusion-spliced Portion of Optical Fiber)

The splice reinforcing portion 50 in this embodiment is not limited tothe reinforcement of the fusion-spliced portion 44 in the optical fiberconnector, but can be used for a reinforcement method of pinching andreinforcing a fusion-spliced portion 90, in which end portions 88 and 89of a first optical fiber 91 and a second optical fiber 92 arefusion-spliced to each other, between a pair of reinforcing members 51and 54 as shown in FIGS. 14 and 15.

The assembling tool 80 shown in FIG. 14 includes a reinforcing memberholding portion 81 holding the second reinforcing member 54 at apredetermined position, a first core holding portion 82 holding a partof the optical fiber core of the first optical fiber 91, an arm portion83 having a bearing portion 84 rotatably holding the shaft portion 60 ofthe first reinforcing member 51, a first pressing cover 85 pressing thepart of the optical fiber core of the first optical fiber 91 against thefirst core holding portion 82 from upside of the first core holdingportion 82, a second core holding portion 86 holding a part of theoptical fiber core of the second optical fiber 92, and a second pressingcover 87 pressing the part of the optical fiber core of the secondoptical fiber 92 against the second core holding portion 86 from upsideof the second core holding portion 86.

A pair of reinforcing members 51 and 54 include adhesion layers 53 and56 which can be depressed at the position where the first optical fiber91 and the second optical fiber 92 come in contact with each other onthe inner surface which comes in contact with the ends portions 88 and89 of the first optical fiber 91 and the second optical fiber 92, asshown in FIGS. 4 to 7. The first reinforcing member 51 includes a shaftportion 60 at one end in the length direction (in the lateral directionin FIG. 14) of the first optical fiber 91 and the second optical fiber92.

The sequence of assembling the splice reinforcing portion 50 by pinchingthe fusion-spliced portion 90 between the pair of reinforcing members 51and 54 is the same as the sequence shown in FIGS. 8 to 12. The result isshown in FIG. 14. The state where the assembled splice reinforcingportion 50 is detached from the assembling tool 80 is shown in FIG. 15.

In this embodiment, the optical fiber cores 91 and 92 are pinchedbetween the core holding portions 82 and 86 and the pressing covers 85and 87, but a part of an optical fiber cord or an optical fiber cablemay be pinched therebetween.

In this way, by using the first reinforcing member 51 having the shaftportion 60 of which the central axis line is perpendicular to the lengthdirection of the optical fibers 91 and 92 and the assembling tool 80having the bearing portion 84, the first reinforcing member 51 falls outin the direction parallel to the length direction of the optical fibers91 and 92 with respect to the second reinforcing member 54 and it isthus possible to suppress a rotational (twisting) force about the axisof the optical fibers when the first reinforcing member 51 comes incontact with the end portions 88 and 89 of the optical fibers 91 and 92.

Since the positional relationship between the reinforcing member holdingportion 81 and the bearing portion 84 are appropriately determined inadvance, the bearing portion 74 supporting the shaft portion 60 can beused as a reference for positioning the first reinforcing member 51 withrespect to the second reinforcing member 54. That is, since the secondreinforcing member 54 is not erroneously moved when attaching the shaftportion 60 to the bearing portion 74, the work is easily carried outeven with the small sizes of the reinforcing members 51 and 54.

While the invention has been described on the basis of an exemplaryembodiment, the invention is not limited to the above-mentionedembodiment, but may be modified in various forms without departing fromthe concept of the invention.

Modification of Optical Fiber Connector

As described above, the external optical fiber to which the opticalfiber connector is applied may not have a tensile fiber. An example ofan optical fiber connector 10A which can be used in this case and whichhas a more simplified constitution is shown in FIGS. 17A and 17B.Hereinafter, FIGS. 17A and 17B are comprehensively referred to as “FIG.17”.

The optical fiber connector 10A can be a tip of an external opticalfiber 45A not having a tensile fiber. The stop ring 38 includes a firsthalf portion 38 a inserted into the plug frame 21 and a second halfportion 38 b to which the boot 65 is attached, and an engaging claw 33which can engage with the engaging window 27 of the plug frame 21 isformed on the outer circumferential surface of the first half portion 38a of the stop ring 38. That is, the stop ring 38 having thisconstitution has a structure in which the stop ring 30 and the screwring 35 shown in FIG. 1 are integrated into a body.

The sequence of assembling the housing or the like is not particularlylimited, but the following sequence may be employed as an example.

As an advance preparation before the fusion splice, the ferrule spring24, the stop ring 38, the external optical fiber boot 65, and theprotective tube 66 are made to pass around the external optical fiber45. These components are preferably arranged on the rear side (the rightside in FIG. 17) so as not to interfere with the fusion splice. The cap11 and the coupling 25 may be attached to the plug frame 21 in advanceor may be attached thereto after the cap 11 and the coupling 25 areattached to the stop ring 38.

As described above, the bare optical fibers 43 and 46 arefusion-spliced, the splice reinforcing portion 50 is assembled thereto(see FIGS. 8 to 13), the plug frame 21 is attached thereto from thefront side (the left side in FIG. 17) of the ferrule 12 to dispose theferrule 12 in the opening 22 of the plug frame 21, the stop ring 38 ispushed into the plug frame 21 to cause the engaging claw 33 to engagewith the engaging window 27, and the ferrule spring 24 is received alongwith the ferrule 12 and the splice reinforcing portion 50. The boot 65is attached to the second half portion 38 b of the stop ring 38. Theoptical fiber connector 10A shown in FIG. 17 can be assembled throughthis sequence.

In this way, in the optical fiber connector 10A according to thismodification, since the external optical fiber 45A does not include atensile fiber, the assembling sequence is more simplified than theoptical fiber connector 10 shown in FIG. 1.

Second Embodiment

An optical fiber connector 110 according to a second embodiment of theinvention will be described below.

FIGS. 23A and 23B show an optical fiber connector 110 according to thesecond embodiment of the invention and FIGS. 24A and 24B show animportant part of the optical fiber connector 110. The optical fiberconnector 110 has a constitution in which the other end portion 43 of aninserted optical fiber 40 of which one end portion 42 is fixed to aferrule 12 (optical fiber connector ferrule) is fusion-spliced to afront end portion 46 of an external optical fiber 45 and a splicereinforcing portion 50 in which the fusion-spliced portion 44 is pinchedand reinforced between a pair of reinforcing members 51 and 54 isreceived in a housing or the like. FIGS. 23A and 23B may becomprehensively referred to as “FIG. 23”. Similarly, FIGS. 24A and 24Bmay be comprehensively referred to as “FIG. 24”.

In the following description, in order to distinguish both sides in thelength direction (the lateral direction in FIG. 23) of an optical fiber,the side which a joint end face 14 of the ferrule 12 faces (the leftside in FIG. 23) may be referred to as “forward” or “front” and theopposite side (the right side in FIG. 23) may be referred to as“backward”, “rear”, or “toward a base end”. The front-rear direction isthe length direction at one end portion 42 of the inserted optical fiber40 and is also a joint direction when the optical fiber connector 110 isjointed to the opposite optical fiber connector.

An external optical fiber 45 is formed of an optical transmission mediumsuch as an optical fiber cord or an optical fiber cable having anoptical fiber. In this embodiment, the external optical fiber 45 is anoptical fiber cord including a multi-core optical fiber core 47including an optical fiber tape core in which a plurality optical fibers(optical fiber wires, which are not shown) are arranged in parallel inthe lateral direction perpendicular to the length direction thereof, atubular sheath 48 surrounding the multi-core optical fiber core 47, anda tensile fiber 49 received between the optical fiber core 47 and thesheath 48. In the front end portion 46 of the external optical fiber 45,the resin coating of the optical fiber core 47 and the resin coating ofthe optical fiber wires are removed and each of a plurality of bareoptical fibers (parts of core and clad) are separated.

Examples of the number of bare optical fibers 46 (the number of cores)included in the optical fiber core 47 include 2, 4, 8, and 12. In FIGS.23A, 24A, and 25, the 12-core constitution is simplified and only 4cores are shown. The optical fiber cord in this embodiment has aconstitution in which a single optical fiber tape core is received in asheath, but is not particularly to this constitution. For example, aconstitution in which a plurality of single-core optical fiber cores arereceived in a single sheath, a constitution in which a plurality ofoptical fiber tape cores are received in a single sheath, and aconstitution in which one or more optical fiber tape cores andsignal-core optical fiber cores are received in a single sheath can beemployed as the constitution of the external optical fiber.

The sheath 48 is formed of a resin such as polyethylene and preferablyhas flexibility. A plurality of tensile fibers 49 extend along thelength direction of the optical fiber and functions as a tensile memberaccepting a tensile force (tension) to the optical transmission medium.The fiber material used for the tensile fiber 49 is not particularlylimited as long as it can provide a necessary tensile strength, andexamples thereof include aramid fiber, glass fiber, and carbon fiber.

The tensile member or the sheath is not essential to the invention. Forexample, an optical fiber core or an optical fiber tape core not havinga sheath may be used as the external optical fiber. In some structuresof an optical fiber cable or the like, metal wires such as steel wiresor various wires such as fiber-reinforced plastics (FRP) may be used asthe tensile member. Examples of the optical fiber cable include anoptical drop cable and an optical indoor cable.

The inserted optical fiber 40 is an optical fiber of which one endportion 42 is fixed to the ferrule 12 and of which the other end portion43 protrudes (extends) backward from the ferrule 12. In this embodiment,the inserted optical fiber 40 includes a multi-core optical fiber core41 which is an optical fiber tape core, and the resin coating of theoptical fiber core 41 and the resin coating of the optical fiber wiresare removed in one end portion 42 and the other end portion 43 of theoptical fiber core 41 so as to separate into a plurality of bare opticalfibers (parts of cores and clad).

The front end of the inserted optical fiber 40 is exposed from the jointend face 14 and is butt-jointed to an optical fiber of the oppositeoptical fiber connector.

The optical fiber used as the inserted optical fiber 40 is not limitedto the multi-core optical fiber, but a structure in which one or moreshort single-core optical fibers are inserted into a single ferrule, astructure in which one or more optical fiber tape cores and single-coreoptical fiber cores are received in a single ferrule, or the like may beemployed.

As shown in FIG. 25, the other end portion 43 of the inserted opticalfiber 40 and the front end portion 46 of the external optical fiber 45correspond to each other in a one-to-one manner and are fusion-splicedto each other. As shown in FIG. 24, the fusion-spliced portion 44 of theother end portion 43 of the inserted optical fiber 40 and the front endportion 46 of the external optical fiber 45 is pinched and reinforcedbetween a pair of reinforcing members 51 and 54 in the splicereinforcing portion 50.

The reinforcing members 51 and 54 include reinforcing member bodies 52and 55 formed of a hard material such as resin or metal and adhesionlayers 53 and 56 disposed on the inner surfaces which come in contactwith the other end portion 43 of the inserted optical fiber 40 and thefront end portion 46 of the external optical fiber 45.

The ferrule 12 around the inserted optical fiber 40 is not shown in FIG.25, but one end portion 42 of the inserted optical fiber 40 ispreferably fixed into an optical fiber insertion hole 13 of the ferrule12 before the fusion-splice to the external optical fiber 45.

As shown in FIGS. 18, 23, and 24, the ferrule 12 includes a front endface (joint end face) 14 butt-jointed to a ferrule (not shown) ofanother optical fiber connector (the opposite optical fiber connector),a rear end face 16 which is the opposite end face of the joint end face14, optical fiber insertion holes (micro holes) 13 opened in the jointend face 14, and a boot-receiving hole 17 opened in the rear end face16. The ferrule 12 can be formed, for example, as an integrated moldedproduct formed of plastic.

The joint end face 14 of the ferrule 12 may be a vertical faceperpendicular to the central axis (substantially matched with theoptical axis of the optical fiber 42) of the optical fiber insertionholes 13, or may be an inclined face inclined in a predetermineddirection corresponding to a ferrule of another optical fiber connector.

The optical fiber insertion holes 13 are formed in the same number asthe number of optical fibers in one end portion 42 of the insertedoptical fiber 40. For example, a method of injecting an adhesive intothe optical fiber insertion holes 13 to adhere to the bare opticalfibers can be simply used as the method of fixing the bare opticalfibers which are one end portion 42 of the inserted optical fiber 40 tothe ferrule 12. The optical fiber insertion holes 13 are connected tothe boot-receiving hole 17. A ferrule boot 18 is attached around theoptical fiber core 41 and is received in the boot-receiving hole 17. Theferrule boot 18 is preferably formed of a flexible material such asrubber or elastomer, but the ferrule boot 18 may be formed of a materialsuch as a resin or a metal having low flexibility.

Examples of the number of optical fiber insertion holes 13 (the numberof cores) formed in the ferrule 12 include 2, 4, 8, and 12 and depend onthe number of cores of the optical fiber core 47. In the optical fiberconnector 110 according to this embodiment, a single-core ferrule may beused as the ferrule 12.

The optical fiber insertion holes 13 on the joint end face 14 of themulti-core ferrule 12 are arranged in a line to match with thearrangement of optical fibers pinched between the reinforcing members 51and 54. The invention is not limited to the constitution in which thearrangement of optical fibers in the ferrule 12 is set to be the same asthe arrangement of optical fibers in the splice reinforcing portion 50,but the arrangement of optical fibers separated for each core betweenthe ferrule 12 and the splice reinforcing portion 50 may be changed.

As shown in FIG. 24B, a ferrule boot 18 covering the portion of theinserted optical fiber 40 protruding from the ferrule 12 is attached tothe ferrule 12. The pair of reinforcing members 51 and 54 (specifically,the bodies 52 and 55 thereof) includes protrusions serving as bootclamping portions 52 a and 55 a at the ends close to the ferrule 12 andthe ferrule boot 18 is clamped between the boot clamping portions 52 aand 55 a.

Accordingly, both ends of the ferrule boot 18 are tightly held betweenthe ferrule 12 and the pair of reinforcing members 51 and 54, therebymore satisfactorily preventing the warp or damage of the insertedoptical fiber 40.

A guide pin 15 of which the front end portion protrudes forward from thejoint end face 14 is provided to the ferrule 12 for the purpose of thepositioning with respect to the ferrule of the opposite optical fiberconnector.

The guide pin 15 is inserted into a guide pin insertion hole 15 apassing through the joint end face 14 and the rear end face 16 and isinserted into a guide pin insertion hole (not shown) formed in theferrule of another optical fiber connector to suppress the misalignmentin the direction along the joint end face 14 (such as the verticaldirection in FIG. 24A, the vertical direction in FIG. 24B, or aninclined direction obtained by combining the directions) and accuratelyalign the optical fiber connector 110 and the opposite optical fiberconnector.

The positioning type relative to the opposite optical fiber connectorusing the guide pin 15 is called a guide pin positioning type.

As shown in FIG. 24A, the guide pin insertion holes 15 a and 15 a enablethe guide pin 15 to detachably be inserted thereto (inserted and pulledout) and is formed in the front-rear direction.

In this embodiment, two guide pin insertion holes 15 a are formed andare formed on both sides, respectively, of the optical fiber insertionhole 13 through which the inserted optical fiber 40 is inserted.

The guide pins 15 are inserted into the pair of guide pin insertionholes 15 a.

As shown in FIG. 22, the guide pin 15 has a substantially tubularcylinder shape and includes a body portion 190 having a tapered frontend portion 190 a and a base end portion 191 formed at the rear endthereof.

The base end portion 191 includes a neck portion 192 extending backwardfrom the rear end of the body portion 190 and a head portion 193 formedat the rear end of the neck portion 192. The front surface of the headportion 193 serves as a locking end portion 193 a coming in contact witha front plate portion 177 of a pin clamp 19 to be described later.

The body portion 190, the neck portion 192, and the head portion 193 allhave a substantially cylindrical shape and the central axis directionsthereof are matched with each other.

The neck portion 192 has a diameter smaller than that of the headportion 193. Hereinafter, the neck portion 192 may be referred to as asmall-diameter portion and the head portion 193 may be referred to as alarge-diameter portion. The body portion 190 has a diameter larger thanthat of the neck portion 192.

As shown in FIGS. 23 and 24, the body portion 190 is inserted throughthe guide pin insertion hole 15 a and the front end portion thereofprotrudes forward from the joint end face 14.

As shown in FIG. 24A, the base end portion of the guide pin 15 protrudesfrom the rear end face 16 of the ferrule 12 and the base portion 191which is the protruding portion is held in the pin clamp 19.

The optical fiber connector 110 shown in FIG. 23 is of a type (maletype) having a guide pin 15, but may be of a type (female type) nothaving a guide pin 15 as described later.

As shown in FIGS. 18, 23, and 24, the pin clamp 19 is disposed on theside of the rear end face 16 of the ferrule 12. The pin clamp 19 isdisposed on the front side of the fusion-spliced portion 44.

As shown in FIGS. 19 to 21, the pin clamp 19 serves to support the guidepin 15 and is detachably attached to the base end portion 191 of theguide pin 15 protruding from the rear end face 16 of the ferrule 12.

The pin clamp 19 shown in the drawings is formed of a synthetic resinmaterial and has a substantially U shape having a bottom portion 171 andside wall portions 172 and 172 formed on both sides of the bottomportion 171. The space surrounded with the bottom portion 171 and theside wall portions 172 and 172 serves as an insertion space 173 throughwhich the inserted optical fiber 40 is inserted (see FIGS. 23 and 24).

The insertion space 173 can be formed to receive the ferrule boot 18.That is, by setting the distance between the side wall portions 172 and172 to be substantially equal to or slightly smaller than the width ofthe ferrule boot 18, both edges of the ferrule boot 18 contact the innersurfaces of the side wall portions 172 and 172 to position the ferruleboot.

In the below description, the extending direction of the side wallportions 172, that is, the upward direction in FIG. 21, may be referredto as upward (or the height direction) and the opposite directionthereof may be referred to as downward. The vertical direction in FIG.21 is a direction substantially perpendicular to the formation directionof the guide pin insertion hole 15 a through the guide pin 15 isinserted.

The side wall portion 172 includes an outer plate portion 175, an innerplate portion 176 formed with a gap inward from the outer plate portion175, a front plate portion 177 formed at a front edge of the bottomportion 171, and a rear plate portion 178 formed at a rear edge of thebottom portion 171.

The outer plate portion 175 is substantially vertically upright from theside edge of the bottom portion 171 with respect to the bottom portion171.

The inner plate portion 176 is substantially vertically upright withrespect to the bottom portion 171 and the space between the outer plateportion 175 and the inner plate portion serves as a reception portion179 receiving the head portion 193 of the guide pin 15.

The inner plate portion 176 is formed to be lower than the outer plateportion 175. The bottom surface 179 a of the reception portion 179 maybe a curved surface along the outer circumference of the head portion193.

As shown in FIGS. 19 to 21, the front plate portion 177 is substantiallyvertically upright from the front edge of the bottom portion 171 withrespect to the bottom portion 171. Accordingly, the front plate portion177 is substantially perpendicular to the front-rear direction.

A locking recessed portion 183 is formed downward from the upper edge177 a of the front plate portion 177. The locking recessed portion 183shown in the drawings has a substantially U shape and the bottom portion183 a which is the deepest portion is located to be higher than thebottom surface 179 a of the reception portion 179.

As shown in FIG. 21, since the locking recessed portion 183 is formeddownward from the upper edge 177 a, it can receive the neck portion 192of the guide pin 15 moving downward.

Since the outer plate portion 175, the inner plate portion 176, and therear plate portion 178 are formed to extend substantially upward, thereception portion 179 surrounded therewith can receive the head portion193 moving downward.

Accordingly, the neck portion 192 and the head portion 193 of the guidepin 15 can go into and from the locking recessed portion 183 and thereception portion 179 in the vertical direction in FIG. 21.

In the example shown in the drawings, the locking recessed portion 183is formed downward (that is, in the direction substantiallyperpendicular to the formation direction of the guide pin insertion hole15 a), but the formation direction of the locking recessed portion 183is not limited to this direction and may be any direction as long as itis a direction crossing the formation direction of the guide pininsertion hole 15 a. For example, the formation direction may be adirection inclined by an angle greater than 0° and less than 90° in thevertical direction in FIG. 21.

As shown in FIGS. 20 and 21, the width W1 of the locking recessedportion 183 is larger than the outer diameter of the neck portion 192 ofthe guide pin 15 and smaller than the outer diameter of the head portion193, the locking recessed portion 183 regulates the forward movement ofthe head portion 193 and regulates the movement of the guide pin 15 inthe direction.

That is, as shown in FIG. 20, when a force toward the front end(downward in FIG. 20) is applied to the guide pin 15, a locking endportion 193 a which is the front face of the head portion 193 comes incontact with the rear face 177 a of the front plate portion 177, therebypreventing the forward movement of the head portion 193. Accordingly, itis possible to prevent the falling of the guide pin 15.

The rear plate portion 178 is formed substantially vertically uprightfrom the rear edge of the bottom portion 171 with respect to the bottomportion 171. The outer edge of the rear plate portion 178 reaches therear edge of the outer plate portion 175. In the example shown in thedrawing, the rear plate portion 178 has substantially the same height asthe outer plate portion 175.

The rear plate portion 178 or the front plate portion 177 can beconfigured to regulate the backward movement of the guide pin 15. Thatis, the rear plate portion 178 or the front plate portion 177 can beconfigured to prevent the backward movement of the guide pin 15 bybringing the rear face 190 b of the body portion 190 into contact withthe front plate portion 177 or bringing the head portion 193 intocontact with the rear plate portion 178, when a force to the rear side(upward in FIG. 20) is applied to the guide pin 15.

As shown in FIG. 20, a positioning protuberance portion 181 protrudingbackward is formed on the rear face 178 a of the rear plate portion 178.

As shown in FIG. 23, the positioning protuberance portion 181 serves toprevent the misalignment of the ferrule spring 24 and is inserted intothe front end portion of the ferrule spring 24.

The rear face 178 a of the rear plate portion 178 serves as a springseat 20 for accepting an impelling force (pressing force based onelasticity) from the ferrule spring 24. Accordingly, even when the guidepin 15 is not installed in the ferrule 12, the pin clamp 19 is attachedto the ferrule 12. The pin clamp 19 can be inserted into and fixed tothe ferrule 12 by, for example, irregularity or the like (not shown).

The optical fiber connector 110 described in this embodiment is amulti-core optical fiber connector and the example shown in the drawingsis an MPO type optical fiber connector (F13 type multi-core opticalfiber connector defined in the JIS C5982, MPO: Multi-fiber Push On). Theoptical fiber connector applicable to the invention is not limited tothe single-core type or the multi-core type.

The housing 11 of the optical fiber connector 110 includes a sleeve-like(tubular) plug frame 21 and a sleeve-like (tubular) stop ring 30attached to the rear end of the plug frame 21.

The ferrule 12 is inserted through the opening 22 at the front end ofthe plug frame 21.

An engaging claw 33 which can engage with an engaging window 27 formedin the side wall portion of the plug frame 21 is formed in the outersurface of the stop ring 30 so as to integrate the plug frame 21 and thestop ring 30 into a body.

The ferrule spring 24 (impelling means) serves to impel the ferrule 12forward through the use of the pin clamp 19 and is disposed around thesplice reinforcing portion 50, the front end of the spring 24 is broughtinto contact with the spring seat 20 at the rear end of the pin clamp19, and the rear end of the spring 24 is brought into contact with thespring seat 31 at the front end of the stop ring 30.

When the joint end face 14 of the ferrule 12 is jointed to a ferrule ofanother optical fiber connector, the ferrule 12 is guided in the opening22 and pushed backward to contract the ferrule spring 24, an appropriateforce acts between the joint end face 14 of the ferrule 12 and a jointend face of a ferrule of another optical fiber connector, therebybringing the joint end faces into close contact with each other. Whenthe joint between the ferrule 12 and the ferrule of another opticalfiber connector is released, the ferrule spring 24 is stretched and theferrule 12 moves in the opening 22 and is restored to the originalposition.

An engaging portion 23 used for the MPO type connector plug to engagewith an engaging claw (not shown) of an MPO type connector adaptor or areceptacle is disposed on both sides (both side in the verticaldirection in FIG. 23A) in the width direction of the plug frame 21. Acoupling 25 is disposed on the outer circumference of the plug frame 21,and a pair of coupling springs 26 and 26 is received between the outercircumferential surface of the plug frame 21 and the innercircumferential surface of the coupling 25. Accordingly, the coupling 25can move forward and backward relative to the plug frame 21 with thestretching and contracting of the coupling springs 26 and 26. Theengaging portion 23 or the coupling 25 has the same constitution asdefined in the JIS or the like as the MPO type connector plug.

When the invention is applied to different types of optical fiberconnectors, the constituents required for the joint (connector joint) ofthe optical fiber connectors are installed in the ferrule or thehousing.

A through-hole 32 passing in the front-rear direction (the lateraldirection in FIG. 23) along the length direction of the optical fiber isformed in the stop ring 30. The cross-sectional shape (the sectionalshape in the plane perpendicular to the length direction of the opticalfiber) of the through-hole 32 has at least a size which can receive theshape of the cross-sectional shape of the splice reinforcing portion 50.Accordingly, when the stop ring 30 is pushed in toward the plug frame 21from the rear side of the splice reinforcing portion 50 in a state wherethe ferrule 12 is inserted into the opening 22 of the plug frame 21, thestop ring 30 is prevented from interfering with the splice reinforcingportion 50 (hindering the push thereof). When the stop ring 30 is pushedin toward the plug frame 21 from the rear side of the splice reinforcingportion 50, the engaging claw 33 is drawn into the splice reinforcingportion 50 just before the engaging claw 33 reaches the engaging window27. Accordingly, on the back surface side of the engaging claw 33, agroove 32 a is formed in the inner surface of the through-hole 32,thereby avoiding the interference of the splice reinforcing portion 50with the back surface of the engaging claw 33.

An external screw 34 is formed on the outer circumferential surface ofthe rear end portion of the stop ring 30. An internal screw 36 formed onthe inner circumferential surface of the screw ring 35 can be fastenedto the external screw 34. The front end portion of the tensile fiber 49of the external optical fiber 45 can be pinched and fixed between theexternal screw 34 and the internal screw 36. The screw ring 35 includesan opening 37 at the rear end thereof, and a part of the tensile fiber49 of the external optical fiber 45 and the optical fiber core 47 isinserted into the opening 37. The cross-sectional shape (the sectionalshape in the plane perpendicular to the length direction of the opticalfiber) of the opening 37 preferably has a certain opening size so as toavoid the contact of the tensile fiber 49 with the splice reinforcingportion 50.

A boot 65 for an external optical fiber for protecting the externaloptical fiber 45 is attached to the outer circumferential surface of thescrew ring 35. The boot 65 is generally formed of a flexible materialsuch as rubber or elastomer. In this embodiment, a protective tube 66 isattached around the sheath 48 of the external optical fiber 45 and anannular locking portion 67 having a large diameter at the front endportion of the tube 66 is inserted into the boot 65.

The sequence of assembling the housing or the like is not particularlylimited, but the following sequence can be employed as an example.

As an advance preparation before the fusion splice, the ferrule spring24, the stop ring 30, the screw ring 35, the external optical fiber boot65, and the protective tube 66 are made to pass around the externaloptical fiber 45. These components are preferably arranged on the rearside (the right side in FIG. 23) so as not to interfere with the fusionsplice.

The bare optical fibers 43 and 46 are fusion-spliced and thefusion-spliced portion 44 is pinched and reinforced between the pair ofreinforcing members 51 and 54 in the splice reinforcing portion 50.

As shown in FIGS. 19 and 21, the locking recessed portion 183 of the pinclamp 19 is formed downward and thus can cause the neck portion 192 ofthe guide pin 15 to go into and away from the vertical direction.

Accordingly, as shown in FIG. 18, by upward moving the pin clamp 19indicated by a virtual line, it is possible to fit the neck portion 192of the guide pin 15 into the locking recessed portion 183. At this time,the head portion 193 is received in the reception portion 179.

Accordingly, the pin clamp 19 is disposed at the rear end of the ferrule12 in the state where the base end portion 191 of the guide pin 15 isheld therein.

As shown in FIGS. 20 and 21, since the width W1 of the locking recessedportion 183 is smaller than the outer diameter of the head portion 193.Accordingly, when the forward force (downward in FIG. 20) is applied tothe guide pin 15, the locking end portion 193 a which is the front faceof the head portion 193 comes in contact with the rear face 177 a of thefront plate portion 177, thereby stopping the forward movement of thehead portion 193. Accordingly, the forward movement of the guide pin 15is regulated.

When a backward (upward in FIG. 20) force is applied to the guide pin15, the rear face 190 b of the body portion 190 comes in contact withthe front plate portion 177 or the head portion 193 comes in contactwith the rear plate portion 178, thereby regulating the backwardmovement of the guide pin 15.

The plug frame 21 is attached from the front side (the left side in FIG.23) of the ferrule 12 to dispose the ferrule 12 in the opening 22 of theplug frame 21, the stop ring 30 is pushed into the plug frame 21 tocause the engaging claw 33 to engage with the engaging window 27, andthe ferrule spring 24 is received along with the ferrule 12 and thesplice reinforcing portion 50. The coupling 25 may be attached to theplug frame 21 in advance or may be attached thereto after the coupling25 is attached to the stop ring 30.

The front end portion of the tensile fiber 49 is placed on the externalscrew 34 of the stop ring 30 and the internal screw 36 of the screw ring35 is fastened to the external screw 34 to fix the front end portion ofthe tensile fiber 49. When the front end portion of the tensile fiber 49extends over the outer circumference of the plug frame 21, the tensilefiber is cut out if necessary. The boot 65 is attached to the stop ring30. The optical fiber connector 110 shown in FIG. 23 can be assembledthrough this sequence.

When the external optical fiber does not include a tensile fiber, theinternal screw 36 of the screw ring 35 is fastened to the external screw34 of the stop ring 30 to integrate the housing into a body, withoutpinching the tensile fiber.

The optical fiber connector 110 shown in FIG. 23 is of a type (maletype) having a guide pin 15, but may be of a type (female type) nothaving a guide pin 15.

The sequence of detaching the guide pin 15 from the optical fiberconnector 110 of the type (male type) shown in FIG. 23 to acquire theoptical fiber connector 110 of the type (female type) not having theguide pin 15 will be described below with reference to FIGS. 26 to 28.

In the reverse sequence of the above-mentioned sequence, the plug frame21 is detached to expose the ferrule 12 and the pin clamp 19.

As described above, the locking recessed portion 183 of the pin clamp 19can allow the neck portion 192 of the guide pin 15 to go into and fromthe locking recessed portion in the vertical direction in FIG. 21.Accordingly, as shown in FIGS. 26 and 27, when the pin clamp 19 is moveddownward, the neck portion 192 is pulled out of the locking recessedportion 183.

Accordingly, the guide pin 15 can move in the length direction and canbe pulled out toward the front end.

As shown in FIG. 28, the pin clamp 19 is moved upward after pulling outthe guide pin 15, and then is disposed at the rear end of the ferrule12. By attaching the plug frame 21 again, it is possible to obtain theoptical fiber connector 110 of the type (female type) not having theguide pin 15.

The optical fiber connector 110 not having the guide pin 15 has the sameconstitution as the optical fiber connector 110 shown in FIG. 23, exceptthat the guide pin 15 is not provided. In such a type of optical fiberconnector 110, the guide pin insertion hole 15 a serves as an insertionhole into which a guide pine of the opposite optical fiber connector isinserted.

When it is intended to change the optical fiber connector 110 of thetype (female type) not having the guide pin 15 to the type (male type)having the guide pin 15, the guide pin 15 has only to be attached to theferrule 12 in the opposite sequence of the above-mentioned sequence.

In the optical fiber connector 110, the pin clamp 19 includes thelocking recessed portion 183 and the locking recessed portion 183 canallow the neck portion 192 of the guide pin 15 to go into and from thelocking recessed portion in the direction substantially perpendicular tothe guide pin insertion hole 15 a. Accordingly, by moving the pin clamp19 in the direction, it is possible to release the movement regulationin the length direction of the guide pin 15 and to separate the guidepin 15.

Therefore, the type (male type) having the guide pin 15 and the type(female type) not having the guide pin 15 can be easily switched to eachother, thereby improving the workability on the splicing site.

In separation of the guide pin 15, since it is not necessary to move thepin clamp 19 backward, the fusion-spliced portion 44 of the insertedoptical fiber 40 and the external optical fiber 45 is not adverselyinfluenced. Therefore, it is not necessary to guarantee a space formovement of the pin clamp 19 between the ferrule 12 and thefusion-spliced portion 44, thereby reducing the size in the lengthdirection of the optical fiber connector 110.

Since the pin clamp 19 includes the locking recessed portion 183 towhich the base end portion 191 of the guide pin 15 is locked, it ispossible to prevent the guide pin 15 from falling out toward the frontend.

In this embodiment, the fusion-spliced portion 44 of the insertedoptical fiber 40 and the external optical fiber 45 is pinched between apair of reinforcing members 51 and 54 in the splice reinforcing portion50, but the invention is not limited to this constitution. Aconstitution in which the fusion-spliced portion 44 is reinforced with aknown reinforcing sleeve may be employed.

Another splicing method such as a method (mechanical splice method) ofbutt-jointing optical fibers of a pair of elements of a clamp unit maybe used for the splicing of the inserted optical fiber 40 and theexternal optical fiber 45.

FIGS. 29 and 30 show another example of the pin clamp and the pin clamp119 shown in the drawings is different from the pin clamp 19 shown inFIGS. 19 to 21, in that an extension 182 having a holding protrusion 184is formed in the front plate portions 177 and 177.

The extension 182 is formed at the upper edges of the front plateportions 177 and 177 so as to extend upward from the further innerposition than the locking recessed portion 183.

The holding protrusion 184 is formed at the inner edge of the extension182 so as to protrude inward (in a direction in which both holdingprotrusions get closer to each other).

As shown in FIG. 30, since the distance between the front ends of theholding protrusions 184 and 184 is smaller than the width of the ferruleboot 18, the holding protrusion 184 can regulate the upward movement(outward movement) of the ferrule boot 18 in the insertion space 173.Accordingly, the pin clamp 119 can be prevented from falling out of theferrule boot 18.

The top surface 184 a of the holding protrusion 184 is an inclined faceslowly going down toward the protruding direction (inward). Accordingly,when the ferrule boot 18 is inserted into the insertion space 173, theferrule boot 18 presses the top face 184 a outward to move the holdingprotrusions 184 outward with the warping deformation of the front plateportions 177, thereby enabling the insertion of the ferrule boot 18.

Hereinafter, a cap-attached optical fiber connector, an optical fiberconnector assembling method, and an optical fiber connector capaccording to embodiments of the invention will be described withreference to the accompanying drawings.

Third Embodiment

A third embodiment of the invention will be described below.

FIG. 31 shows a cap-attached optical fiber connector 210A according tothis embodiment.

In the cap-attached optical fiber connector 210A, an optical fiberconnector cap 150 (hereinafter, may be simply referred to as a cap) isdetachably attached to a front end portion (an end portion of the sideon which a ferrule 211 is disposed) of an optical fiber connector 210assembled to the terminal of an optical fiber cord 2 (opticaltransmission medium).

In FIGS. 31, 32A, and 32B, the left side in the cap-attached opticalfiber connector 210A and the optical fiber connector 210 is defined as afront side and the right side is defined as a rear side.

Hereinafter, FIGS. 32A and 32B may be comprehensively referred to as“FIG. 32”. Similarly, FIGS. 40A and 40B may be comprehensively referredto as “FIG. 40”, FIGS. 42A and 42B may be comprehensively referred to as“FIG. 42”, FIGS. 43A and 43B may be comprehensively referred to as “FIG.43”, and FIGS. 45A and 45B may be comprehensively referred to as “FIG.45”.

The optical fiber connector 210 shown in FIG. 31 is a single-coreoptical fiber connector.

The optical fiber connector 210 is a so-called site-assembled opticalfiber connector.

As shown in FIGS. 31, 32A, and 32B, the optical fiber connector 210schematically includes a ferrule 211 having a structure in which aflange portion 211 b protrudes on the outer circumference of a capillarymember 211 a, an inserted optical fiber 212 which is a short opticalfiber inserted into and fixed to the ferrule 211 (specifically, thecapillary member 211 a), a sleeve-like housing 214 receiving anoptical-fiber-attached ferrule 213 including the ferrule 211 and theinserted optical fiber 212 inserted into and fixed to the ferrule 211(specifically, the capillary member 211 a), a spring 215 that isreceived in the housing 214 and that elastically impels theoptical-fiber-attached ferrule 213 to the front side (hereinafter, alsoreferred to as a connector front side) relative to the housing 214, anda screwed ring member 216 screwed to a tensile member fixing tube 214 a(to be described later) which is a rear end portion of the housing 214opposite to the front end portion in which the ferrule 211 is disposed.

The optical fiber connector 210 further includes a boot 217 externallyinserted onto the screwed ring member 216 and disposed to extendbackward from the screwed ring member 216.

As shown in FIG. 38, in the optical fiber connector 210, a sleeve-likegrin 218 (coupling) may be externally inserted and attached to thehousing 214. The grip 218 is disposed in the housing 214 to slide withina movable range in the front-rear direction.

In FIG. 38, the optical fiber connector having the grip 218 disposedtherein is referenced by reference sign 210B.

In the housing 214, a sleeve-like stop ring 142 is inserted into andfixed to the rear end portion of a sleeve-like plug frame 141 tointegrate them into a body. The stop ring 142 is disposed to extendbackward from the plug frame 141. The rear end portion of the stop ring141 located in the back of the plug frame 141 serves as the tensilemember fixing tube 214 a of the housing 214.

The tensile member fixing tube 214 a has an external screw 214 b (screwportion) formed on the outer circumference thereof, and the screwed ringmember 216 having an internal screw 216 a which can be screwed to theexternal screw 214 b can be screwed thereto from the rear side of thetensile member fixing tube 214 a, as shown in FIG. 31.

Hereinafter, the tensile member fixing tube 214 a is also referred to asa screwed tube.

A ferrule, a plug frame, and a grip of a single-core optical fiberconnector (plug) such as an SC type optical fiber connector (F04 typeoptical fiber connector defined in the JIS C5973; SC: Single fiberCoupling optical fiber connector) and an MU type optical fiber connector(F14 type optical fiber connector defined in the JIS C5983, MU:Miniature-Unit coupling optical fiber connector) can be employed as theferrule 211, the plug frame 141, and the grip 218.

The inserted optical fiber 212 of the optical-fiber-attached ferrule 213includes a rear extension 212 c which is a portion extending to the rearend opposite to the joint end face 211 c (front end face) for butt jointwhich is a front end of the capillary member 211 a of the ferrule 211.The inserted optical fiber 212 is inserted into and fixed to thecapillary member 211 a of the ferrule 211 in a state where the end faceof the end portion (front end portion) opposite to the rear extension212 c is arranged on the polished joint end face 211 c of the endportion of the capillary member 211 a.

As shown in FIG. 31, in the optical fiber connector 210 assembled to theterminal of the optical fiber cord 2, a spliced portion 3 where the endportion (the rear end portion of the inserted optical fiber 212) of therear extension 212 c of the inserted optical fiber 212 is opticallyspliced to the front end portion of an optical fiber 2 a drawn out ofthe terminal of the optical fiber cord 2 is received in the housing 214.

The optical fiber 2 a of the optical fiber cord 2 is a single-corecoated optical fiber in which a bare optical fiber 2 d is coated with aresin coating material 2 e (hereinafter, also simply referred to as acoating material) so as to cover the outer circumference thereof and tointegrate into a body.

On the other hand, the inserted optical fiber 212 is a single-corecoated optical fiber (specifically, an optical fiber core) from of whichboth ends a bare optical fiber 2 a is drawn out, for example, as shownin FIG. 35. The inserted optical fiber 212 is bonded and fixed to theferrule 211 (specifically, the capillary member 211 a) with an adhesivedisposed in a fiber hole 211 d in a state where one of both protrudingportions of a coated portion coated with a coating material 12 b out ofthe bare optical fiber 12 a is inserted into a positioning hole 211 dawhich is a front part (on the side of the joint end face 211 c) of thefiber hole 211 d penetrating the capillary member 211 a of the ferrule211 and which has an opening in the joint end face 211 c and the coatedportion is inserted into a coated portion receiving hole 211 d 2 whichis a rear part of the fiber hole 211 d about the positioning hole 211 d1 and which has a diameter larger (an inner diameter larger) than thatof the positioning hole 211 d 1.

The optical fibers 2 a and 212 are a single-core optical fiber coreherein, but for example, an optical fiber wire may be employed.

The inserted optical fiber 212 may be a bare optical fiber all over thelength.

As shown in FIG. 35, the coated portion of the inserted optical fiber212 has a part extending backward from the ferrule 211.

As shown in FIG. 35, the spliced portion 3 is a fusion-spliced portionin which the rear end of the inserted optical fiber 212 of theoptical-fiber-attached ferrule 213 and the front end of the opticalfiber 2 a extending from the terminal of the optical fiber cord 2 arefusion-spliced. Hereinafter, when the spliced portion 3 indicates thefusion-spliced portion, it may be referred to as a fusion-splicedportion.

The fusion-spliced portion 3 is specifically, a fusion-spliced portionin which the bare optical fiber drawn out from the rear end portion ofthe inserted optical fiber 212 and the bare optical fiber 2 d drawn outfrom the front end portion of the optical fiber 2 a extending from theterminal of the optical fiber cord 2 are fusion-spliced.

A fusion reinforcing portion (spliced point reinforcing portion)incorporating a reinforcing member (not shown) covering thefusion-spliced portion 3 to the fusion-spliced portion 3 as a body andreinforcing the fusion-spliced portion is received in the housing 214 ofthe optical fiber connector 210.

In the optical fiber connector 210, a part, which extends from a sheath2 c, of a fiber-like tensile member 2 b (hereinafter, also referred toas a tensile fiber) longitudinally added to the optical fiber 2 a andreceived along with the optical fiber 2 a in the resin sheath 2 c(external sheath) of the optical fiber cord 2 is pinched and fixedbetween the outer circumferential surface of the screwed tube 214 a atthe rear end of the housing 214 and the inner circumferential surface ofthe screwed ring member 216 screwed to the screwed tube 214 a, wherebythe optical fiber cord 2 is detained relative to the housing 214.

A cap 150 will be described below.

As shown in FIGS. 31, 32A, and 32B, the cap 150 has a constitution inwhich a hooking protrusion 152 (tensile member detaining portion) usedto detain the tensile fiber 2 b extending from the terminal of theoptical fiber cord 2 in the work of assembling the optical fiberconnector 210 to the terminal of the optical fiber cord 2 protrudes fromthe outer surface of a body 151 (hereinafter, also referred to as a capbody) of a bottomed cylinder which is detachably externally insertedonto the front end portion (the front end portion of the plug frame 141)of the housing 214 of the optical fiber connector 210.

The cap body 151 of the cap 150 shown in the drawings includes abottomed cylinder of which one end in the axis direction of a tubularbody portion 151 a which can be externally inserted onto the front endportion of the housing 214 of the optical fiber connector 210 is blockedby an end wall 151 b, and is externally inserted onto the front endportion of the housing 214 so as to be attached to and detached from thehousing.

The hooking protrusion 152 protrudes to be inclined about the axis lineof the tubular body portion 151 a so that as it goes from the tubularbody portion 151 a of the cap body 151 to the front end blocked by theend wall 151 b of the cap body 151, the distance from the outercircumferential surface of the tubular body portion 151 a increases.

In the cap 150 shown in the drawings, the hooking protrusions 152protrude from both sides with the axis line of the tubular body portion151 a of the cap body 151 interposed therebetween.

The cap 150 is a plastic molded product and can be produced at a lowcost.

A method of assembling the optical fiber connector 210 to the terminalof the optical fiber cord 2 (an optical fiber connector assemblingmethod) will be described below.

First, as shown in FIG. 35, a fusion-splicing and reinforcing step(fiber splicing step) of fusion-splicing the rear end of the insertedoptical fiber 212 of the optical-fiber-attached ferrule 213 assembled inadvance to the front end of the optical fiber 2 a extending from theterminal of the optical fiber cord 2 and assembling a splice reinforcingportion (spliced portion reinforcing portion) for reinforcing thefusion-spliced portion formed by the fusion splice by the use of areinforcing member 3 is performed.

For example, a reinforcing sleeve 4 shown in FIGS. 36 and 37 can besuitably used as the splice reinforcing portion.

As shown in FIGS. 36 and 37, the reinforcing sleeve 4 includes aheat-shrinkable tube 4 a and a thermoplastic resin layer 4 b disposedalong the inner surface thereof, and further includes a rod-like tensilemember 4 c (metal rod) inserted over the whole length in the lengthdirection (axis line direction) of the heat-shrinkable tube 4 a with thesame thickness as the heat-shrinkable tube 4 a.

In assembling the fusion-spliced portion using the reinforcing sleeve 4,as shown in FIG. 35, the inserted optical fiber 212 and the opticalfiber 2 a of the optical fiber cord 2 are fusion-spliced, thereinforcing sleeve 4 externally inserted onto the optical fiber cord 2in advance is moved to the ferrule 211 and covers the fusion-splicedportion 3, the rear extension 212 c of the inserted optical fiber 212,and the portion, which extends from the terminal of the optical fibercord 2, of the optical fiber 2 a of the optical fiber cord 2, as shownin FIG. 37, and the reinforcing sleeve 4 is heated in this state to melta thermoplastic resin forming the thermoplastic resin layer 4 b and tothermally contract the heat-shrinkable tube 4 a. By cooling (forexample, cooling with air), the thermoplastic resin in the molted stateis solidified. Accordingly, the fusion-spliced portion 3 is embedded inthe solidified thermoplastic resin, and the heat-shrinkable tube 4 a,the thermoplastic resin therein, and the fusion-spliced portion 3 areintegrated into a body, whereby it is possible to assemble the fusionsplice reinforcing portion in which the fusion-spliced portion 3 isreinforced with the heat-shrinkable tube 4 a, the thermoplastic rein,and the rod-like tensile member 4 c.

The heat-shrinkable tube 4 a is formed of a heat-shrinkable resin and,for example, polyolefin contracting at 100° C. to 160° C. can be used.

A hot-melt resin (hot-melt adhesive) can be suitably used as thethermoplastic resin forming the thermoplastic resin layer 4 b. Examplesof the hot-melt resin include ethylene-vinyl acetate copolymer (EVA),polyethylene, polyisobutylene, polyamide, and ethylene-ester acrylatecopolymer. It is preferable that the thermoplastic resin be softened atthe contraction temperature of the heat-shrinkable tube 4 a. Thesoftening temperature is, for example, in the range of 100° C. to 160°C.

In FIG. 37, one end in the length direction of the reinforcing sleeve 4is externally inserted onto a rear end tube 211 e at the rear end of theferrule 211, and the heat-shrinkable tube 4 a is fixed to the rear endtube 211 e at the rear end of the ferrule 211 when the reinforcingsleeve 4 is heated to assemble the fusion splice reinforcing portion,whereby the ferrule with the fusion splice reinforcing portion in whichthe fusion splice reinforcing portion is integrated to the rear side ofthe ferrule 211 is assembled. However, the invention is not limited tothis constitution, but the reinforcing sleeve 4 may be disposed at aposition separated backward (toward the optical fiber cord 2) from theferrule 211 and the fusion splice reinforcing portion not integrated tothe ferrule 211 may be assembled at the position separated backward fromthe ferrule 211.

The inserted optical fiber 212 extends backward from the rear end tube211 e through the inside of the rear end tube 211 e.

When the fusion splicing and reinforcing step is ended, as shown in FIG.32A, a housing assembling step of fitting the stop ring 142 to the plugframe 141 to assemble the housing 214 and receiving theoptical-fiber-attached ferrule 213, the fusion splice reinforcingportion, and the spring 215 (coil spring) in the housing 214 isperformed.

In the housing assembling step, the spring 215 and the stop ring 142externally inserted onto the optical fiber cord 2 in advance is movedtoward the ferrule 211, the ferrule 211, the fusion splice reinforcingportion, the spring 215, and the stop ring 142 are inserted into thesleeve-like plug frame 141 from the rear end, and the engaging claw 142b protruding from the outer circumference of the stop ring 142 is lockedto the engaging recessed portion 141 a formed in the inner surface ofthe rear end portion of the plug frame 141, whereby the front sleeveportion 142 a located in the front of the screwed tube 214 a of the stopring 142 is fitted to the plug frame 141.

As a result, the stop ring 142 is fixed to the plug frame 141, and theferrule 211, the fusion splice reinforcing portion, and the spring 215are received in the sleeve-like housing 214 in which the plug frame 141and the stop ring 142 are integrated into a body.

In the ferrule 211, the capillary member 211 a is inserted into a frontend opening 141 c guaranteed inside a front end convex wall 141 bprotruding on the inner circumference of the front end portion of theplug frame 141 so as to be movable in the axis line direction of theplug frame 141 and is received in the front end portion of the housing214 so as to be movable in the axis line direction of the housing 214.By bringing the flange portion 211 b into contact with the front endconvex wall 141 b inside the housing 214, the capillary member isprevented from falling out forward from the housing 214.

The spring 215 is locked so as not to fall out backward from the stopring 142 by the spring receiving wall 142 c protruding in the rear endportion of the stop ring 142. In the ferrule 211, the flange portion 211b is disposed at the position where it comes in contact with the frontend convex wall 141 b of the plug frame 141 with the elastic impellingforce of the spring 215 and can be pushed into the rear side of thehousing 214 against the elastic impelling force of the spring 215.

When the housing 214 is assembled in the housing assembling step, asshown in FIG. 32A, a tensile member fixing step of fitting the cap body151 of the cap 150 to the front end portion of the housing 214 to attachthe cap 150 to the housing 214, hooking and detaining the tensile fiber2 b extending from the optical fiber cord 2 to and in the hookingprotrusion 152 of the cap 150, and screwing the screwed ring member 216to the screwed tube 214 a at the rear end of the housing 214 (FIG. 32B)to fix the tensile fiber 2 b to the screwed tube 214 a is carried out.

In the housing assembling step, when the assembling of the housing 214is completed, the terminal of the optical fiber cord 2 is disposed at aposition separated backward from the housing 214.

In the tensile member fixing step, the front end portion of the tensilefiber 2 b being drawn out from the terminal of the optical fiber cord 2along with the optical fiber 2 a in advance and extending from theterminal of the optical fiber cord 2 is attached to and detained in thehooking protrusion 152 of the cap 150 attached to the front end portionof the housing 214, for example, by winding, binding, or the like.

In this specification, the winding or the binding is considered tocorrespond to the “hooking” of the tensile fiber 2 b on the hookingprotrusion 152 of the cap 150.

For example, as shown in FIG. 34, in the tensile fiber 2 b extendingfrom the terminal of the optical fiber cord 2, a loop portion 2 g inwhich the front end portion thereof is formed in a loop and a knot 2 fcausing the tensile fiber 2 b to hold the loop portion 2 g may be formedand then the loop portion 2 g may be externally inserted onto and hookedon the hooking protrusion 152.

As described above, the hooking protrusion 152 protrudes to be inclinedabout the axis line of the tubular body portion 151 a so that as it goesfrom the tubular body portion 151 a of the cap body 151 to the front endblocked by the end wall 151 b of the cap body 151, the distance from theouter circumferential surface of the tubular body portion 151 aincreases. Accordingly, there is an advantage that it is difficult toallow the tensile fiber 2 b hooked on the hooking protrusion 152 bywinding, binding, or the like to fall out of the hooking protrusion 152.

The tensile fiber 2 b is hooked on and fixed to the hooking protrusion152, whereby tension is applied to the part extending between theterminal of the optical fiber cord 2 and the hooking protrusion 152.

For example, aramid fiber can be suitably used for the tensile fiber 2 bbut, for example, glass fiber and carbon fiber may be used in additionto the aramid fiber.

A plurality of tensile fibers 2 b are received in the sheath 2 c of theoptical fiber cord 2. In this case, in detaining the tensile fibers 2 bin the hooking protrusion 152 of the cap 150 attached to the front endportion of the housing 214 by the hooking, specifically, a plurality oftensile fibers 2 b extending from the terminal of the optical fiber cord2 are partitioned into two parts with the optical fiber 2 a interposedtherebetween to form two tensile fiber sets 2 h with substantially thesame thickness and the front end portions of the tensile fiber sets 2 hare hooked on two hooking protrusions 152 of the cap 150, respectively.

When the detainment of the tensile fibers 2 b in the hooking protrusions152 of the cap 150 by the hooking is completed, the screwed ring member216 externally inserted onto the optical fiber cord 2 in advance ismoved toward the housing 214 and the screwed ring member 216 is screwedto the outer circumference of the screwed tube 214 a at the rear endportion (the rear end portion of the stop ring 142) of the housing 214,as shown in FIG. 32B.

As described above, the terminal of the optical fiber cord 2 is disposedat the position separated backward from the housing 214. Accordingly,when the screwed ring member 216 is screwed to the outer circumferenceof the screwed tube 214 a, two tensile fiber sets 2 h extending forwardfrom the terminal of the optical fiber cord 2 through the vicinity ofthe external screw 214 b of the screwed tube 214 a can be pinched andfixed between the outer circumferential surface of the screwed tube 214a and the inner circumferential surface of the screwed ring member 216.The tensile fiber sets 2 h are specifically pinched between the externalscrew 214 b of the screwed tube 214 a and the internal screw 216 a ofthe screwed ring member 216 and thus can be strongly fixed to the rearend portion of the housing 214.

When the tensile member fixing step is ended, the parts of the tensilefiber sets 2 h from the position at which they are fixed to the housing214 by the use of the screwed ring member 216 to the cap 150 areremoved, and the sleeve-like boot 217 externally inserted onto theoptical fiber cord 2 in advance is moved toward the housing 214 andexternally fitted and attached to the screwed ring member 216 (see FIG.31). Accordingly, it is possible to totally assemble the optical fiberconnector 210.

Since the cap 150 is attached to the front end portion of the assembledoptical fiber connector 210, it is possible to obtain a cap-attachedoptical fiber connector 210A at the same time as assembling the opticalfiber connector 210. Since the cap 150 attached to the optical fiberconnector 210 covers the joint end face 211 c at the front end of thecapillary member 211 a of the ferrule 211 of the optical fiber connector210 by the use of the cap body 151, the cap can be made to function as aprotective cover protecting the joint end face 211 c of the ferrule 211by holding the state where it is attached to the optical fiber connector210.

The terminal of the optical fiber cord 2 is disposed in an inner hole217 a penetrating the boot 217 disposed to extend backward from thescrewed ring member 216.

Since the tensile fibers 2 b extending from the terminal of the opticalfiber cord 2 are fixed to the screwed tube 214 a at the rear end of thehousing 214 through the use of the screwed ring member 216, the terminalis detained without falling out to the rear side of the connector fromthe sleeve-like boot 217 disposed to extend backward from the screwedring member 216.

The grip 218 shown in FIG. 38 can be attached to the outside of thehousing 214 so as to slide within a movable range in the front-reardirection guaranteed by externally inserting the grip to the housing 214from the front side (connector front side) of the optical fiberconnector 210.

When it is intended to install the grip 218 in the optical fiberconnector 210 with the cap 150 attached thereto, that is, thecap-attached optical fiber connector 210A shown in FIG. 31, having beencompletely assembled to the terminal of the optical fiber cord 2, thecap 150 is detached from the optical fiber connector 210 and the grip218 is externally inserted onto the housing 214 from the front side ofthe optical fiber connector 210.

As described above, in the course of assembling the optical fiberconnector 210 to the terminal of the optical fiber cord 2, by attachingthe cap 150 to the housing 214 in the step of assembling the housing214, the front end portions of the tensile fiber sets 2 h extending fromthe terminal of the optical fiber cord 2 can be hooked on (wound on orbound to) and detained in the hooking protrusion 152 of the cap 150 andthus tension can be applied to the tensile fiber sets 2 h.

Accordingly, without using a conventional swaging tool, the work offixing the tensile fiber sets 2 h to the rear end of the housing 214 canbe carried out in the state where tension is applied to the tensilefiber sets 2 h.

Fourth Embodiment

A fourth embodiment of the invention will be described below.

As shown in FIG. 39, an optical fiber connector 20 according to thisembodiment is different from the optical fiber connector 210 accordingto the third embodiment, in that the ferrule 211 directly attached tothe front end of the optical fiber 2 a drawn out from the terminal ofthe optical fiber cord 2 instead of the optical-fiber-attached ferrule213 described in the third embodiment is received in the housing 214.

The constitutions other than the constitution in which the ferrule 211directly attached to the front end of the optical fiber 2 a is receivedin the housing 214 are equal to those of the optical fiber connector 210according to the third embodiment.

The front end of the optical fiber 2 a drawn out from the terminal ofthe optical fiber cord 2 is inserted into the ferrule 211. As shown inFIG. 41, the optical fiber 2 a is attached and fixed to the ferrule 211by inserting the bare optical fiber 2 d drawn out from the front endthereof into the positioning hole 211 d 1 (see FIG. 35) of the fiberhole 211 d of the ferrule 211 and inserting the front end portion of thecoated portion coated with the coating material 2 e into the coatedportion receiving hole 211 d 2. The joint end face 211 c of the ferrule211 is polished, for example, after the optical fiber 2 a is insertedand fixed.

The optical fiber connector 20 is assembled by attaching the ferrule 211to the front end of the optical fiber 2 a, assembling the housing 214 toreceive the ferrule 211 and the spring 215 as shown in FIG. 40A, fixingthe tensile fiber sets 2 h of the optical fiber cord 2 to the screwedtube 214 a of the rear end portion of the housing 214 through thesequence of the tensile member fixing step described in the thirdembodiment as shown in FIGS. 40A and 40B, and then externally insertingand fixing the tensile fiber sets to the screwed ring member 216attached to the rear end portion (the screwed tube 214 a) of the housing214.

As shown in FIGS. 40A and 40B, since the work of fixing the tensilefiber sets 2 h of the optical fiber cord 2 to the screwed tube 214 a ofthe rear end portion of the housing 214 is performed in the state wherethe tensile fiber sets 2 h are hooked on and detained in the hookingprotrusions 152 protruding from the cap body 151 of the cap 150 attachedto the front end portion of the housing 214 through the sequence of thetensile member fixing step described in the third embodiment, it ispossible to obtain a cap-attached optical fiber connector 20A in whichthe cap 150 is attached to the front end portion of the optical fiberconnector 20 at the same time as the assembly of the optical fiberconnector 20 is completed.

Fifth Embodiment

A fifth embodiment of the invention will be described below.

The invention may be applied to the assembling of the optical fiberconnector to the terminal of a multi-core optical fiber cord (opticaltransmission medium).

FIG. 42 shows an optical fiber connector 100 according to thisembodiment and FIG. 43 shows an important part of the optical fiberconnector 100. The optical fiber connector 100 has a constitution inwhich the other end portion 43 of an inserted optical fiber 40 of whichone end portion 42 is fixed to a ferrule 280 is fusion-spliced to afront end portion 46 of an external optical fiber 45 and a spliced pointreinforcing portion 50 in which the fusion-spliced portion 44 is pinchedand reinforced between a pair of reinforcing members 51 and 54 isreceived in a housing or the like.

In the following description, in order to distinguish both sides in thelength direction (the lateral direction in FIG. 42) of an optical fiber,the side which a joint end face 281 of the ferrule 280 faces (the leftside in FIG. 42) may be referred to as “front side” and the oppositeside (the right side in FIG. 42) may be referred to as “rear side”. Thefront side is also referred to as a “front end” and the opposite side(the right side in FIG. 42) thereof is also referred to as a “rear end”.

An external optical fiber 45 is formed of an optical transmission mediumsuch as an optical fiber cord or an optical fiber cable having anoptical fiber. In this embodiment, the external optical fiber 45 is anoptical fiber cord including a multi-core optical fiber core 47including an optical fiber tape core in which a plurality optical fibers(optical fiber wires, which are not shown) are arranged in parallel inthe lateral direction perpendicular to the length direction thereof, atubular sheath 48 (outer shell, externally-inserted film) surroundingthe multi-core optical fiber core 47, and a tensile fiber 49 receivedbetween the optical fiber core 47 and the sheath 48.

In the front end portion 46 of the external optical fiber 45, the resincoating of the optical fiber core 47 and the resin coating of theoptical fiber wires are removed and each of a plurality of bare opticalfibers (parts of core and clad) are separated.

Examples of the number of bare optical fibers 46 (the number of cores)included in the optical fiber core 47 include 2, 4, 8, and 12. In FIG.42A, the 12-core constitution is simplified and only 6 cores are shown.The optical fiber cord in this embodiment has a constitution in which asingle optical fiber tape core is received in a sheath, but is notparticular to this constitution. For example, a constitution in which aplurality of single-core optical fiber cores are received in a singlesheath, a constitution in which a plurality of optical fiber tape coresare received in a single sheath, and a constitution in which one or moreoptical fiber tape cores and signal-core optical fiber cores arereceived in a single sheath can be employed as the constitution of theexternal optical fiber.

Since an alignment mechanism such as a V groove is not necessary for apair of reinforcing members 51 and 54 to be described later, the numberof cores of the optical fiber which are held between a pair ofreinforcing members 51 and 54 is not specified depending on thestructure of a pair of reinforcing members 51 and 54, as long as it canbe received within the width range of adhesion layers 53 and 56. Thespecification of a pair of reinforcing members 51 and 54 applied tooptical fiber connectors with different numbers of cores such as 2cores, 4 cores, 8 cores, and 12 cores can be used in common. That is, bychanging only the ferrule to a ferrule having a suitable number ofcores, an optical fiber connector having a different number of cores canbe constructed, thereby contributing to a decrease in cost.

The sheath 48 is formed of a resin such as polyethylene and preferablyhas flexibility. A plurality of tensile fibers 49 extend along thelength direction of the optical fiber and functions as a tensile memberaccepting a tensile force (tension) to the optical transmission medium.The fiber material used for the tensile fiber 49 is not particularlylimited as long as it can provide a necessary tensile strength, andexamples thereof include aramid fiber, glass fiber, and carbon fiber.

The tensile member or the sheath is not essential to the invention. Forexample, an optical fiber core or an optical fiber tape core not havinga sheath may be used as the external optical fiber. In some structuresof an optical fiber cable or the like, metal wires such as steel wiresor various wires such as fiber-reinforced plastic (FRP) may be used asthe tensile member.

The inserted optical fiber 40 is an optical fiber of which one endportion 42 is fixed to the ferrule 280 and of which the other endportion 43 protrudes (extends) backward from the ferrule 280. In thisembodiment, the inserted optical fiber 40 includes a multi-core opticalfiber core 41 which is an optical fiber tape core, and the resin coatingof the optical fiber core 41 and the resin coating of the optical fiberwires are removed in one end portion 42 and the other end portion 43 ofthe optical fiber core 41 so as to separate into a plurality of bareoptical fibers (parts of cores and clads).

The optical fiber used as the inserted optical fiber 40 is not limitedto the multi-core optical fiber, but a structure in which one or moreshort single-core optical fibers are inserted into a single ferrule, astructure in which one or more optical fiber tape cores and single-coreoptical fiber cores are received in a single ferrule, or the like may beemployed.

As shown in FIG. 44, the other end portion 43 of the inserted opticalfiber 40 and the front end portion 46 of the external optical fiber 45correspond to each other in a one-to-one manner and are fusion-splicedto each other. As shown in FIG. 43, the fusion-spliced portion 44 of theother end portion 43 of the inserted optical fiber 40 and the front endportion 46 of the external optical fiber 45 is pinched between a pair ofreinforcing members 51 and 54 to reinforce the fusion-spliced portion.The ferrule 280 around the inserted optical fiber 40 is not shown inFIG. 44, but one end portion 42 of the inserted optical fiber 40 ispreferably fixed into an optical fiber insertion hole 283 (fiber hole)of the ferrule 280 before the fusion-splice to the external opticalfiber 45.

As shown in FIG. 43, the ferrule 280 includes a front end face (jointend face) 281 butt-jointed to a ferrule (not shown) of another opticalfiber connector, a rear end face 282 which is the opposite end face ofthe joint end face 281, optical fiber insertion holes (micro holes) 283opened in the joint end face 281, and a boot-receiving hole 287 openedin the rear end face 282. The ferrule 280 can be formed, for example, asan integrated molded product formed of plastic. The joint end face 281of the ferrule 280 may be a vertical face perpendicular to the centralaxis (substantially matched with the optical axis of the optical fiber42) of the optical fiber insertion holes 283, or may be an inclined faceinclined in a predetermined direction corresponding to a ferrule ofanother optical fiber connector.

The optical fiber insertion holes 283 are formed in the same number asthe number of optical fibers in one end portion 42 of the insertedoptical fiber 40. For example, a method of injecting an adhesive intothe optical fiber insertion holes 283 to adhere to the bare opticalfibers can be simply used as the method of fixing the bare opticalfibers which are one end portion 42 of the inserted optical fiber 40 tothe ferrule 280. The optical fiber insertion holes 283 are connected tothe boot-receiving hole 287. A ferrule boot 288 is attached around theoptical fiber core 41 and is received in the boot-receiving hole 287.The ferrule boot 288 is preferably formed of a flexible material such asrubber or elastomer, but the ferrule boot 288 may be formed of amaterial such as a resin or a metal having low flexibility.

Examples of the number of optical fiber insertion holes 283 (the numberof cores) formed in the ferrule 12 include 2, 4, 8, and 12. In FIG. 42A,the structure of 280 cores is simplified and only 6 cores are shown. Inthe optical fiber connector 100 according to this embodiment, asingle-core ferrule may be used as the ferrule 280.

The optical fiber insertion holes 283 on the joint end face 281 of themulti-core ferrule 280 are arranged in a line to match with thearrangement of optical fibers pinched between the reinforcing members 51and 54 to be described later. The invention is not limited to theconstitution in which the arrangement of optical fibers in the ferrule280 is set to be the same as the arrangement of optical fibers in thesplice reinforcing portion 50, but the arrangement of optical fibersseparated for each core between the ferrule 280 and the splicereinforcing portion 50 may be changed.

For the purpose of alignment when coupling the ferrule 280 to anotherferrule of another optical fiber connector, a guide pin 285 passingthrough the joint end face 281 and the rear end face 282 may be provided(a pin fitting positioning type). The tip of the guide pin 285 protrudesfrom the joint end face 281 and the guide pin is inserted into a guidepin insertion hole (not shown) formed in the ferrule of another opticalfiber connector to suppress the shaking in the direction along the jointend face 281 (such as the vertical direction in FIG. 43A, the verticaldirection in FIG. 43B, or an inclined direction obtained by combiningthe directions). When a guide pin is provided to a ferrule of anotheroptical fiber connector, a guide pine insertion hole is provided to theferrule 280. A hole formed as a trace of pulling out the guide pin 285from the ferrule 280 may be used as the guide pin insertion hole 285 a.Alternatively, the ferrule 280 having a guide pin insertion hole formedthereon instead of the guide pin 285 may be used at the first time.

Preferably, the guide pin 285 can be attached and detached by theinsertion and the pulling-out into and from the guide pin insertion hole285 a, since it can be easily determined on the splicing site with whichof the optical fiber connector 100 and another optical fiber connectorto provide the guide pin. For example, when the jointed state of theoptical fiber connector 100 and another optical fiber connector isreleased, a pin clamp 19 is disposed on the rear end face 282 of theferrule 280 so as to prevent the guide pin 285 from beingunintentionally pulled out. In this embodiment shown in FIG. 42, the pinclamp 19 fills a gap between the ferrule 280 and the splice reinforcingportion 50 and includes a spring seat 20 for accepting an impellingforce (pressing force based on elasticity) from a ferrule spring 24.Accordingly, even when the guide pin 285 is not installed in the ferrule280, the pin clamp 19 is attached to the ferrule 280. The pin clamp 19can be inserted into and fixed to the ferrule 280 by, for example,irregularity or the like (not shown).

The guide pin 285 may be fixed to the guide pin insertion hole 285 a(for example, by adhesion or embedment through insert molding) for use.

An example of the reinforcing members 51 and 54 (pinch members) used inthis embodiment is shown in FIGS. 45 to 48. The first reinforcing member51 used in the upper side of FIG. 43B is shown in FIG. 45A and thesecond reinforcing member 54 used in the lower side of FIG. 43B is shownin FIG. 45B. In this embodiment, the reinforcing members 51 and 54includes reinforcing member bodies 52 and 55 (pinch member bodies)formed of a hard material such as a resin or a metal and adhesion layers53 and 56 disposed on the inner surfaces coming in contact with theother end portion 43 of the inserted optical fiber 40 and the front endportion 46 of the external optical fiber 45, respectively.

As shown in FIG. 49, the adhesion layers 53 and 56 are depressed at theposition where the inserted optical fiber and the external optical fiber(which are comprehensively represented by the optical fibers F in FIG.49) come in contact with each other to closely adhere to the outercircumferential surfaces of the optical fibers F in the vicinity of thefusion-spliced portion 44. Accordingly, a mechanism such as a V grooveor a U groove used to align the optical fibers is not necessary to formin the inner surfaces of the reinforcing members. In this embodiment,since the other end portion 43 of the inserted optical fiber 40 and thefront end portion 46 of the external optical fiber 45 are fusion-splicedin advance, the splice loss is small and the loss is not increased dueto the axial misalignment (misalignment of the optical axes) of bothoptical fibers or the separation of the end faces.

In the case of the groove-like mechanism such as a V groove or a Ugroove, when the outer diameter in the vicinity of the fusion-splicedportion 44 is greater than the original outer diameter of the opticalfibers (before the fusion splice), an excessive pressing force acts onthe fusion-spliced portion 44, thereby shortening the lifetime. On theother hand, when the outer diameter in the vicinity of thefusion-spliced portion 44 is smaller, the positioning of the opticalfibers is not stabilized and the positions of the optical fibers may bemisaligned in the lateral direction in the grooved mechanism. On thecontrary, when the adhesion layers 53 and 56 have deformabilityfollowing the outer circumferential surface of the optical fibers F, thepositioning of the optical fibers F is stabilized, thereby suppressingthe warp of the optical fibers F with the lapse of time or the increasein loss.

In this embodiment, as shown in FIG. 49, at the position where theoptical fibers F in the fusion-spliced portion 44 are pinched between apair of reinforcing members 51 and 54, the adhesion layers 53 and 56 ofthe pair of reinforcing members 51 and 54 closely adhere to each otheron both sides (on both sides in the width direction perpendicular to thelength direction) of the optical fibers F. Accordingly, it is possibleto suppress the warp of the optical fibers F with the lapse of time orthe increase in loss. Since there is no gap between the opposed adhesionlayers 53 and 56, it is possible to prevent the permeation of moistureor the like which may adversely influence the lifetime of bare opticalfibers (particularly, in the case of quartz optical fibers). When anopaque material is used for the adhesion layers 53 and 56, it ispossible to prevent the leakage of light (leaking light) from the gapbetween the adhesion layers 53 and 56.

The adhesion layers 53 and 56 are preferably formed of a flexibleelastic material such as rubber or elastomer. Accordingly, when theoptical fibers F are pinched between the adhesion layers 53 and 56 witha pressing force, the adhesion layers are depressed at the positionwhere they come in contact with the optical fibers F and thus moreclosely adhere to the outer circumferential surfaces of the opticalfibers F with the elastic force of the adhesion layers 53 and 56. Theelastic force of the adhesion layers 53 and 56 has such a magnitude thatthe original flat surface is restored, when the pressing force isreleased after the depression.

When a foamed material is used for the adhesion layers 53 and 56, it ispreferable that bubbles be small and the bubbles be independent of eachother (the bubbles be not connected). An adhesive (pressure-sensitiveadhesive) may be used as the adhesion layers 53 and 56, but it ispreferable that the adhesion layers 53 and 56 be non-adhesive (theadhesive force is small or zero to such an extent that the bare opticalfibers 43 and 46 can be easily detached after the temporary disposing)so as to dispose the bare optical fibers 43 and 46 again aftertemporarily disposing them. When the adhesive force of the surfaces ofthe adhesion layers 53 and 56 is weak, it is difficult to cause theadhesion layers 53 and 56 to closely adhere to the bare optical fibers43 and 46. Accordingly, it is preferable that the positionalrelationship between the first reinforcing member 51 (the first pinchmember) and the second reinforcing member 54 (the second pinch member)be fixed to maintain appropriate pressing forces from both sides.

As shown in FIGS. 45 to 47, a pair of reinforcing members 51 and 54includes protuberance portions 61 and recessed portions 62,respectively, engaging with each other on both sides in the widthdirection (the direction perpendicular to the paper surface of FIGS. 46and 47) which is the direction perpendicular to the length direction ofthe inserted optical fiber 40 and the external optical fiber 45. Bycausing the protuberance portions (engaging protuberance portions) 61and the recessed portions (engaging recessed portions) 62 to engage witheach other, the state where the adhesion layers 53 and 56 of the pair ofreinforcing members 51 and 54 closely adhere to each other ismaintained. Accordingly, even when the adhesion therebetween is notmaintained with only the adhesive force between the adhesion layers 53and 56, it is possible to cause the adhesion layers 53 and 56 tosatisfactorily closely adhere to each other and thus to prevent thefirst reinforcing member 51 and the second reinforcing member 54 frombeing separated from each other.

In this embodiment, as shown in FIG. 45B, the body 55 of the secondreinforcing member 54 includes a bottom portion 57 and side wallportions 58 and 58 formed on both sides in the width direction thereofand the engaging recessed portion 62 is a through-hole formed in theside wall portions 58. Accordingly, it is possible to easily confirm theengagement state of the engaging recessed portions 61 from the outsidewith the naked eye or a magnifier. From the viewpoint of theincorporation of the reinforcing members 51 and 54, only the innersurfaces of the side wall portions 58 to form holes (blind holes) notpenetrating the outer surface as the engaging recessed portions. Insteadof forming the engaging protuberance portions in the first reinforcingmember and forming the engaging recessed portions in the secondreinforcing member 54, the engaging protuberance portions may be formedin the second reinforcing member and the engaging recessed portions maybe formed in the first reinforcing member 54. Various combinations suchas a combination of alternately forming the engaging protuberanceportion and the engaging recessed portion in the first reinforcingmember and alternately forming the engaging recessed portion and theengaging protuberance portion in the second reinforcing member so as tobe complementary thereto may be employed.

The side wall portion 58 of the second reinforcing member 54 is dividedinto a plurality of parts (tongue-shaped parts) by cutouts 59 and one orless engaging recessed portions 62 are disposed on one side.Accordingly, as shown in FIG. 48, when the first reinforcing member 51is interposed between the pair of side wall portions 58 opposed to eachother in the width direction, the side wall portions 58 having theengaging recessed portions 62 can be independently opened and closed.Even when a set of engaging portions is loosened, the other engagingportions are not loosened therewith. In the front end portions (theupper side of FIG. 48) of the side wall portions 58 protruding from thebottom wall portion 57, an inclined surface 58 a is formed on the innersurface side of the side wall portion 58. Accordingly, it is possible toeasily interpose the first reinforcing member 51 between the pair ofside walls 58 opposed to each other in the width direction. When theengaging protuberance portions 61 and the engaging recessed portions 62are disengaged from each other after the pair of reinforcing members 51and 54 are combined, a tool may be inserted into the clearance betweenthe inclined surface 58 a of the side wall portion 58 and the firstreinforcing member body 52 to easily push and open the side wall portion58 to the outside in the width direction.

The adhesion layers 53 and 56 in this embodiment include swelledportions 53 a and 56 a of which the surface is raised higher in thevicinity of the fusion-spliced portion 44 and thus the pressing forcecan be kept higher between the swelled portions 53 a and 56 a.Alleviated portions 53 b and 56 b which are lower in height than theswelled portions 53 a and 56 a and which are alleviated in pressingforce are disposed on both sides of the swelled portions 53 a and 56 a(on both sides in the length direction of the bare optical fibers 43 and46). Examples of a method of forming the swelled portions 53 a and 56 ainclude a method of forming protrusions in the reinforcing member bodies52 and 55 in the back of the adhesion layers 53 and 56 and a method ofpartially increasing the thicknesses of the adhesion layers 53 and 56.

The sets of engaging portions including the sets of the engagingprotuberance portions 61 and the engaging recessed portions 62 aredisposed in the length direction of the optical fibers. Specifically,one set (or two or more sets) is disposed at the position of the swelledportions 53 a and 56 a, one set (or two or more sets) is disposed at theposition of the alleviated portions 53 b and 56 b on the side of theinserted optical fiber 40, and one set (or two or more sets) is disposedat the position of the alleviated portions 53 b and 56 b on the side ofthe external optical fiber 45. Accordingly, the pressing force appliedto the fusion-spliced portion 44 from the swelled portions 53 a and 56 acan be adjusted by adjusting the positional relationship of the engagingportions in the swelled portions 53 a and 56 a. Even when the pressingforce of the swelled portions 53 a and 56 a is excessively strong andthe engaging portions are loosened due to the repulsive force betweenthe swelled portions 53 a and 56 a, the engaging portions in thealleviated portions 53 b and 56 b are not loosened well, therebypreventing the first reinforcing member 51 and the second reinforcingmember 54 from being separated from each other.

As shown in FIG. 43B, a ferrule boot 288 covering the part of theinserted optical fiber 40 extending from the ferrule 280 is attached tothe ferrule 280. The pair of reinforcing members 51 and 54(specifically, the bodies 52 and 55 thereof) include protrusions servingas boot clamping portions 52 a and 55 a at ends close to the ferrule 280and the ferrule boot 288 is clamped between the boot clamping portions52 a and 55 a. Accordingly, both ends of the ferrule boot 288 is tightlyheld between the ferrule 280 and the pair of reinforcing members 51 and54, thereby satisfactorily preventing the warp or damage of the insertedoptical fiber 40.

The method of assembling the optical fiber connector 100 according tothis embodiment includes a step of fusion-splicing the other end portion43 of the inserted optical fiber 40, of which one end portion 42 isfixed to the ferrule 280 and of which the other end portion 43 protrudesfrom the ferrule 280, to the front end portion 46 of the externaloptical fiber 45 and then pinching the fusion-spliced portion 44 betweenthe pair of reinforcing members 51 and 54 to integrate them into a body.Accordingly, the adhesion layers 53 and 56 disposed on the innersurfaces of the reinforcing members 51 and 54 can be caused to closelyadhere to the outer circumferential surfaces of the bare optical fibers43 and 46 in the fusion-spliced portion 44.

As shown in FIG. 50, a structure in which the other end portion 43 ofthe inserted optical fiber 40 protruding from the ferrule 280 isfusion-spliced to the front end portion 46 of the external optical fiber45 is prepared. The fusion-spliced portion 44 is pinched between a pairof reinforcing members 51 and 54 to integrate them into a body.

In this embodiment, a ferrule to which the guide pin 285, the ferruleboot 288, the pin clamp 19, and the internal optical fiber 40 areattached in advance is used as the ferrule 280 and the other end portion43 of the inserted optical fiber 40 has only to be fusion-spliced to thefront end portion 46 of the external optical fiber 45 on the splicingsite. When the pin clamp 19 can be attached and detached afterassembling the splice reinforcing portion 50, the assembling work may beperformed in a state where the guide pin 285 or the pin clamp 19 isdetached from the ferrule 280.

By assembling the housing H or the like receiving the ferrule 280 andthe splice reinforcing portion 50 after assembling the splicereinforcing portion 50 to the rear side of the ferrule 280, the opticalfiber connector 100 shown in FIG. 31 can be completed.

The optical fiber connector 100 described in this embodiment is amulti-core optical fiber connector and the example shown in the drawingsis an MPO type optical fiber connector (F13 type multi-core opticalfiber connector defined in the JIS C5982, MPO: Multi-fiber Push On). Theoptical fiber connector applicable to the invention is not limited tothe single-core type or the multi-core type.

The housing H of the optical fiber connector 100 includes a sleeve-like(tubular) plug frame 21 and a sleeve-like (tubular) stop ring 30attached to the rear end of the plug frame 21. The side surface of theferrule 280 is held from the surrounding by the front opening 22 of theplug frame 21. An engaging claw 33 which can engage with an engagingwindow 27 formed in the side wall portion of the plug frame 21 is formedin the outer surface of the stop ring 30 so as to integrate the plugframe 21 and the stop ring 30 into a body. The ferrule spring 24 isdisposed around the splice reinforcing portion 50, the front end of thespring 24 is brought into contact with the spring seat 20 at the rearend of the pin clamp 19, and the rear end of the spring 24 is broughtinto contact with the spring seat 31 at the front end of the stop ring30.

When the joint end face 281 of the ferrule 280 is jointed to a ferruleof another optical fiber connector, the ferrule 280 is guided in theopening 22 and pushed backward to contract the ferrule spring 24, anappropriate force acts between the joint end face 281 of the ferrule 280and a joint end face of a ferrule of another optical fiber connector,thereby bringing the joint end faces into close contact with each other.When the joint between the ferrule 280 and the ferrule of anotheroptical fiber connector is released, the ferrule spring 24 is stretchedand the ferrule 280 moves in the opening 22 and is restored to theoriginal position.

An engaging portion 23 used for the MPO type connector plug to engagewith an engaging claw (not shown) of an MPO type connector adaptor or areceptacle is disposed on both sides (both side in the verticaldirection in FIG. 42A) in the width direction of the plug frame 21. Acoupling 25 is disposed on the outer circumference of the plug frame 21,and a pair of coupling springs 26 and 26 is received between the outercircumferential surface of the plug frame 21 and the innercircumferential surface of the coupling 25. Accordingly, the coupling 25can move forward and backward relative to the plug frame 21 with thestretching and contracting of the coupling springs 26 and 26. Theengaging portion 23 or the coupling 25 has the same constitution asdefined in the JIS or the like as the MPO type connector plug.

When the invention is applied to different types of optical fiberconnectors, the constituents required for the joint (connector joint) ofthe optical fiber connectors are installed in the ferrule or thehousing.

In the optical fiber connector 100 shown in FIG. 42, a cap 290 isprovided to protect the front end portion of the ferrule 280 of theoptical fiber connector plug or the like. The cap 290 is detached in use(at the time of jointing to another optical fiber connector).

The basic structure of the cap 290 is the same as cap 150 described inthe third embodiment.

That is, as shown in FIGS. 42A and 42B and FIGS. 51A to 51C, the cap 290has a constitution in which a hooking protrusion 292 (tensile memberdetaining portion) used to detain the tensile fiber 49 (also referred toas a tensile fiber set) protrudes from the outer surface of a cap body291 of a bottomed cylinder which is detachably externally inserted ontothe front end portion (the front end portion of the plug frame 21) ofthe housing H of the optical fiber connector 100.

The cap body 291 of the cap 290 shown in the drawings includes abottomed cylinder of which one end in the axis direction of a tubularbody portion 291 a which can be externally inserted onto the front endportion of the housing H of the optical fiber connector 100 is blockedby an end wall 291 b, and is externally inserted onto the front endportion of the housing H, that is, the portion of the housing H(specifically, the plug frame 21) protruding more forward from thecoupling 25 so as to be attached thereto and detached therefrom.

The hooking protrusion 292 protrudes to be inclined about the axis lineof the tubular body portion 292 so that as it goes from the tubular bodyportion 292 of the cap body 291 to the front end blocked by the end wall291 b of the cap body 291, the distance from the outer circumferentialsurface of the tubular body portion 292 increases.

In the cap 290 shown in the drawings, the hooking protrusions 292protrude from both sides with the axis line of the tubular body portion292 of the cap body 291 interposed therebetween.

The cap 290 is a plastic molded product and can be produced at a lowcost.

A key groove 291 c fitted to a key 21 a formed on one of the sidesurfaces of the plug frame 21 is formed in the inner surface of the cap291. The key 21 a of the plug frame 21 is conventionally installed toprevent the vertically-reverse use (of the top and bottom in FIG. 42B)of an optical fiber connector plug, and the key groove 291 c of the cap290 is installed on both sides in the vertical direction. Accordingly,it is possible to attach the cap 290 to the optical fiber connector 100without distinguishing the upside and downside of the cap 290.

A through-hole 32 passing in the front-rear direction (the lateraldirection in FIG. 42) along the length direction of the optical fiber isformed in the stop ring 30. The cross-sectional shape (the sectionalshape in the plane perpendicular to the length direction of the opticalfiber) of the through-hole 32 has at least a size which can receive theshape of the cross-sectional shape of the splice reinforcing portion 50.Accordingly, when the stop ring 30 is pushed in toward the plug frame 21from the rear side of the splice reinforcing portion 50 in a state wherethe ferrule 280 is inserted into the opening 22 of the plug frame 21,the stop ring 30 is prevented from interfering with the splicereinforcing portion 50 (hindering the push thereof). When the stop ring30 is pushed in toward the plug frame 21 from the rear side of thesplice reinforcing portion 50, the engaging claw 33 is drawn into thesplice reinforcing portion 50 just before the engaging claw 33 reachesthe engaging window 27. Accordingly, on the back surface side of theengaging claw 33, a groove 32 a is formed in the inner surface of thethrough-hole 32, thereby avoiding the interference of the splicereinforcing portion 50 with the back surface of the engaging claw 33.

An external screw 34 (a screw portion, a male screw) is formed on theouter circumferential surface of the rear end portion of the stop ring30. An internal screw 36 (a female screw) formed on the innercircumferential surface of the screw ring 35 (a screwed ring member) canbe fastened to the external screw 34. The front end portion of thetensile fiber 49 of the external optical fiber 45 can be pinched andfixed between the external screw 34 and the internal screw 36. The screwring 35 includes an opening 37 at the rear end thereof, and a part ofthe tensile fiber 49 of the external optical fiber 45 and the opticalfiber core 47 is inserted into the opening 37. The cross-sectional shape(the sectional shape in the plane perpendicular to the length directionof the optical fiber) of the opening 37 preferably has a certain openingsize so as to avoid the contact of the tensile fiber 49 with the splicereinforcing portion 50.

A boot 65 for an external optical fiber for protecting the externaloptical fiber 45 is attached to the outer circumferential surface of thescrew ring 35. The boot 65 is generally formed of a flexible materialsuch as rubber or elastomer. In this embodiment, a protective tube 66 isattached around the sheath 48 of the external optical fiber 45 and anannular locking portion 67 having a large diameter at the front endportion of the tube 66 is inserted into the boot 65.

The sequence of assembling the housing or the like is not particularlylimited, but the following sequence can be employed as an example.

As an advance preparation before the fusion splice, the ferrule spring24, the stop ring 30, the screw ring 35, the external optical fiber boot65, and the protective tube 66 are made to pass around the externaloptical fiber 45. These components are preferably arranged on the rearside (the right side in FIG. 42) so as not to interfere with the fusionsplice.

As described above, the bare optical fibers 43 and 46 arefusion-spliced, the splice reinforcing portion 50 is assembled thereto,the plug frame 21 is attached thereto from the front side (the left sidein FIG. 42) of the ferrule 280 to dispose the ferrule 280 in the opening22 of the plug frame 21, the stop ring 30 is pushed into the plug frame21 to cause the engaging claw 33 to engage with the engaging window 27,and the ferrule spring 24 is received along with the ferrule 280 and thesplice reinforcing portion 50. The cap 290 and the coupling 25 may beattached to the plug frame 21 in advance or may be attached theretoafter the cap 290 and the coupling 25 are attached to the stop ring 30.

As shown in FIG. 52, the front end portion of the tensile fiber 49passes through the external screw 34 of the stop ring 30 and is hookedon and detained in the hooking protrusion 292 of the cap 290 attached tothe plug frame 21, tension is applied to the tensile fiber 49, and theinternal screw 36 of the screw ring 35 is fastened to the external screw34 in this state to fix the front end portion of the tensile fiber 49.

When the front end portion of the tensile fiber 49 fixed to the stopring 30 extends over the outer circumference of the plug frame 21, thetensile fiber is cut out if necessary. The boot 65 is externallyinserted onto and attached to the screw ring 35 to receive the rear endof the stop ring 30. The optical fiber connector 100 shown in FIG. 42can be assembled through this sequence.

It is possible to obtain a cap-attached optical connector 100A having aconstitution in which the cap 290 is attached to the front end portionof the optical fiber connector 100 at the same time as completing theassembling of the optical fiber connector 100.

The invention is not limited to the above-mentioned embodiments, but maybe appropriately modified in design without departing the concept of theinvention.

(1) A swaging fixing method using a swage ring may be employed as themethod of fixing the tensile fiber to the housing.

For example, as shown in FIGS. 53A and 53B, a constitution may beemployed in which the tensile fiber sets 2 h can be fixed to the housing214A by employing a housing 214A which is formed in a sleeve shapereceiving a ferrule and which has a swage ring attachment portion 214 cin which a swage ring 216A is fixed to the outer circumference thereof,detaining the tensile fiber sets 2 h extending forward from the terminalof the optical transmission medium (the optical fiber cord 2 in FIGS.53A and 53B) through the vicinity of the swage ring attachment portion214 c in the hooking protrusion 152 of the cap 150, and fixing the swagering 216A to the swage ring attachment portion 214 c by swaging in thisstate. A protrusion for partially deforming the swage ring 216A at thetime of swaging and enhancing the fixing force of the tensile fibers isformed to protrude from the outer circumference of the swage ringattachment portion 214 c.

Here, the swaging fixation requires a swaging tool for swaging a swagering, but the fixation of the tensile fiber based on the screwing of ascrewed ring member can be easily embodied by only rotationallyoperating and screwing the screwed ring member to the screw portion,which is advantageous in that no tool is necessary for the fixation ofthe tensile fiber.

(2) The method of optically splicing an optical fiber drawn out from theterminal of an optical transmission medium to an inserted optical fiberinserted into and fixed to a ferrule is not particularly limited. Forexample, a mechanical splicing method of clamping and fixing a pair ofoptical fibers butt-jointed to each other and maintaining thebutt-jointed state may be employed.

(3) The tensile member detaining portion of a cap is not limited to thehooking protrusion, as long as it can detain a tensile fiber.

For example, like the cap 300 shown in FIG. 54, a constitution forpinching and fixing a tensile fiber between the outer surface of a capbody 310 and a pressing plate 330 (the tensile member detaining portion)rotatably disposed on both sides of the cap body 310 with a hingeportion 320 interpose therebetween may be employed. The pressing plate330 of the cap 300 shown in FIG. 54 can maintain the state where it isclosed with respect to the outer surface of the cap body 310 by causingan engaging recessed portion 331 formed in the pressing plate 330 toengage with an engaging claw 311 protruding from the cap body 310

FIGS. 55 to 60 show a specific example of the assembling tool shown inFIGS. 8 to 13.

FIG. 55 is a perspective view of the assembling tool 370. FIG. 56 is aplan view of the assembling tool 370. FIG. 57 is a side view of theassembling tool 370. FIG. 58 is a longitudinal sectional view of theassembling tool 370 and is a sectional view taken along line A1-A1 ofFIG. 56. FIG. 59 is a partially-enlarged plan view of the assemblingtool 370. FIG. 60 is a cross-sectional view of the assembling tool 370and is a sectional view taken along line A2-A2 of FIG. 56.

The assembling tool 370 is used to assemble the splice reinforcingportion 50 and includes a base 376, a reinforcing member holding portion371 holding the second reinforcing member 54 at a predeterminedposition, a core holding portion 372 holding a part of the optical fibercore 47 of the external optical fiber 45, a bearing supporting portion373 having a bearing portion 374 rotatably holding the shaft portion 60of the first reinforcing member 51, and a pressing cover 375 pressingthe part of the optical fiber core 47 of the external optical fiber 45on the core holding portion 372.

Hereinafter, the right side in FIG. 56 may be referred to as a frontside and the opposite side (the left side in FIG. 56) thereof may bereferred to as a rear side. The left-right direction in FIG. 56 may bereferred to as a front-rear direction. In the example shown in thedrawings, the bare optical fibers 43 and 46 and the external opticalfiber 45 are arranged in the front-rear direction (see FIG. 62 and thelike).

As shown in FIGS. 55, 56, and 59, the reinforcing member holding portion371 protrudes upward from the top surface of the base 376 and a holdingrecessed portion 381 holding the second reinforcing member 54 is formedon the top surface thereof. The holding recessed portion 381 is formedto extend along the front-rear direction (the left-right direction inFIG. 56) and can position the second reinforcing member 54 with aposture parallel to the front-rear direction.

As shown in FIG. 59, in this embodiment, a positioning protuberanceportion 381 a protrudes inward from both edges of the holding recessedportion 381 and the second reinforcing member 54 can be fitted betweenthe positioning protuberance portions 381 a and 381 a at both edges.

As shown in FIGS. 55 and 56, the core holding portion 372 protrudesupward from the top surface of the base 376 and the optical fiber core47 of the external optical fiber 45 can be placed on a flat top surface372 a thereof (see FIG. 62 and the like). A pair of regulating recessedportions 383 regulating the movement in the width direction of theexternal optical fiber 45 is formed on the top surface 372 a. Byinterposing the external optical fiber 45 between the regulatingprotuberance portions 383, it is possible to determine the position inthe width direction of the external optical fiber 45.

An insertion recessed portion 384 into which a latch portion 382 of thepressing cover 375 is inserted is formed on the top surface 372 a of thecore holding portion 372.

As shown in FIGS. 55, 56, and 60, the bearing supporting portion 373includes a pair of support members 385 and 385 disposed to oppose eachother. As shown in FIG. 60, the support member 385 is formed in an Lshape having a side plate portion 386 formed upright on the top surfaceof the base 376 and a top plate portion 387 extending outward (in thedirection in which both move separately from each other) from the upperedge of the side plate portion 386.

The side plate portion 386 has a plate shape parallel to the front-reardirection and extends upward (the direction perpendicular to the base376) from the top surface of the base 376. The side plate portions 386and 386 forming a pair are formed to oppose each other. The side plateportions 386 and 386 are preferably elastically bending-deformable sothat the bearing portions 374 and 374 are able to come close to eachother and to move separately from each other.

By setting the distance between the side plate portions 386 and 386 tobe substantially equal to or slightly larger than the width of theoptical fiber core 47, it is possible to position the optical fiber core47 in the width direction.

As shown in FIGS. 57 and 65, the lower part of the front edge of theside plate portion 386 is cut out and thus a stepped portion 386 a isformed at a position slightly higher than the bottom portion of theholding recessed portion 381 in the front edge of the side plate portion386.

As shown in FIGS. 55, 58, 60, and 65, the bearing portion 374 is a holeportion having a substantially circular section formed through at aposition close to the front edge of the side plate portion 386. Thebearing portion 374 has an inner diameter substantially equal to orslightly larger than the outer diameter of the shaft portion 60 and canrotatably support the inserted shaft portion 60. The bearing portions374 and 374 are formed at the opposed positions of the pair of sideplate portions 386 and 386.

An approach groove 388 is formed in the vertical direction in the innersurface of the side plate portion 386. The approach groove 388 is agroove formed to guide the shaft portion 60 of the first reinforcingmember 51 to the bearing portion 374, has a width through which theshaft portion 60 can pass, and extends from the upper edge of the sideplate portion 386 to the bearing portion 374.

As shown in FIGS. 60 and 65, a protuberance portion 388 a is formed onthe bottom portion of the approach groove 388. Since the protuberanceportion 388 a has such a height to make the upward movement of the shaftportion 60 fitted to the bearing portion 374 difficult, the shaftportion 60 fitted to the bearing portion 374 is not easily detached fromthe bearing portion 374.

As shown in FIGS. 55 and 56, the pressing cover 375 has a long plateshape and a base end portion 375 a thereof is hinged to one outer edge372 b of the core holding portion 372. By employing the hinge coupling,the pressing cover 375 can be formed in a body with the core holdingportion 372, which is advantageous in manufacturing cost.

As shown in FIG. 62, the pressing cover 375 rotates about the base endportion 375 a and overlaps with the top surface 372 a of the coreholding portion 372, whereby the optical fiber core 47 can be pinchedbetween the top surface 372 a and the pressing cover.

By inserting the latch portion 382 into the insertion recessed portion384 in a state where the pressing cover 375 overlaps with the topsurface 372 a of the core holding portion 372 and locking the lockingprotuberance portion 382 a to a locking recessed portion (not shown) inthe insertion recessed portion 384, it is possible to maintain the statewhere the optical fiber core 47 is pinched between the pressing cover375 and the top surface.

By elastically bending the latch portion 382 by external work, it ispossible to select the locked state and the unlocked state of thelocking protuberance portion 382 a to and from the locking recessedportion (not shown).

As shown in FIGS. 55 and 56, a positioning protrusion 391 positioning aholding jig 390 holding the ferrule 12 is formed on the front side ofthe reinforcing member holding portion 371. The positioning protrusion391 can regulate the forward movement of the holding jig 390 received inthe reception space 392 between the reinforcing member holding portion371 and the positioning protrusion.

FIGS. 69 and 70 show a pressing jig 393 pressing the first reinforcingmember 51 to the second reinforcing member 54 on the assembling tool370. FIG. 69 is a perspective view of the pressing jig 393 as viewedfrom a side of the top surface and FIG. 70 is a perspective view of thepressing jig 393 as viewed from a side of the bottom surface.

The pressing jig 393 includes a base portion 394 and leg portions 395and 395 vertically extending downward from both edges of the baseportion 394, and a plurality of pressing protuberance portions 396pressing the first reinforcing member 51 are formed on the bottomsurface of the base portion 394. In the example shown in the drawings,the pressing protuberance portions 396 are arranged in two lines alongboth edges of the first reinforcing member 51 and can press the vicinityof the lateral edges of the first reinforcing member 51 at a pluralityof points in the length direction of the first reinforcing member 51.

An example of a method of assembling the splice reinforcing portion 50using the assembling tool 370 will be described below.

As shown in FIGS. 61 and 66, the second reinforcing member 54 with aposture arranged along the front-rear direction is held in the holdingrecessed portion 381 of the reinforcing member holding portion 371.

As shown in FIG. 59, the shift in the width direction of the secondreinforcing member 54 is prevented by the positioning protuberanceportion 381 a.

As shown in FIG. 66, since the upward movement of the bottom wallportion 57 can be suppressed by locating the front end portion 57 a ofthe bottom wall portion 57 of the second reinforcing member 54 below thestepped portions 386 a of the side plate portions 386, the positioningin the vertical direction is possible. By bringing the front end portionof the bottom wall portion 57 or the front end portions of the side wallportions 58 into contact with the side plate portion 386, it is alsopossible to regulate the positional shift in the front-rear direction.

As shown in FIG. 62, a unit (see FIG. 8) in which the other end portion43 of the inserted optical fiber 40 protruding from the ferrule 12 isfusion-spliced to the front end portion 46 of the external optical fiber45 is placed on the assembling tool 370. In the example shown in thedrawing, the ferrule 12 is received and held in the holding jig 390.

The fusion-spliced portion 44 of the bare optical fibers 43 and 46 isplaced on the second reinforcing member 54.

When the holding jig 390 is disposed in the reception space 392 betweenthe reinforcing member holding portion 371 and the positioningprotrusion 391, the movement in the front-rear direction of the holdingjig 390 is regulated and thus the positions in the front-rear directionof the bare optical fibers 43 and 46 on the second reinforcing member 54is determined.

The position in the width direction of the optical fiber core 47 of theexternal optical fiber 45 is determined by placing the optical fibercore on the top surface 372 a of the core holding portion 372 anddisposing the optical fiber core between a pair of regulatingprotuberance portions 383 and 383. The movement in the width directionof the optical fiber core 47 is also regulated by the side plateportions 386 and 386.

By rotationally moving the pressing cover 375 and interposing theoptical fiber core 47 between the pressing cover 375 and the coreholding portion 372, the positional shift of the optical fiber core 47can be prevented. By inserting the latch portion 382 into the insertionrecessed portion 384 and locking the locking protuberance portion 382 ato the locking recessed portion (not shown) in the insertion recessedportion 384, the state where the pressing cover 375 pinches the opticalfiber core 47 is maintained.

By positioning the optical fiber core 47 by the use of the pressingcover 375, it is possible to accurately position the optical fiber core47 and to arrange the optical fiber core 47 in a straight line shape.Accordingly, it is possible to prevent the position shaking of the bareoptical fibers 43 and 46 in the splice reinforcing portion 50 due to thebending of the optical fiber core 47 or the like.

As shown in FIGS. 63 and 67, the shaft portion 60 of the firstreinforcing member 51 is caused to approach the approach groove 388 ofthe side plate portion 386 and is fitted to the bearing portion 374. Theshaft portions 60 and 60 protruding to one side and the other side ofthe first reinforcing member 51 are inserted into the bearing portions374 and 374 of the side plate portions 386 and 386, respectively, andare rotatably supported by the bearing portions 374 and 374.

As shown in FIGS. 64 and 68, by rotationally moving the firstreinforcing member 51 about the shaft portion 60 fitted to the bearingportion 374, the fusion-spliced portion 44 and the bare optical fibers43 and 46 are pinched between a pair of reinforcing members 51 and 54.As shown in FIG. 68, when pinching the fusion-spliced portion 44 betweena pair of reinforcing members 51 and 54, the engaging protuberanceportions 61 are made to engage with the engaging recessed portions 62.Accordingly, it is possible to assemble the splice reinforcing portion50 to the rear side of the ferrule 12.

As shown in FIG. 71, when the first reinforcing member 51 is pressed topinch the fusion-spliced portion 44 and the bare optical fibers 43 and46 between the reinforcing members 51 and 54, the pressing jig 393 maybe placed on the first reinforcing member 51 and the first reinforcingmember 51 may be pressed down through the use of the pressingprotuberance portions 396 (see FIG. 70).

Accordingly, it is possible to press the vicinity of both lateral edgesof the first reinforcing member 51 at a plurality of points along thelength direction of the first reinforcing member 51 and tosatisfactorily cause all the engaging protuberance portions 61 to engagewith the engaging recessed portions 62.

Since all the engaging protuberance portions 61 can be caused to engagewith the engaging recessed portions 62 substantially at the same time bythe use of the pressing jig 393, a large sound is generated at the timeof causing the engaging protuberance portions 61 to engage with theengaging recessed portions 62, whereby the completion of the assemblingof the splice reinforcing portion 50 can be easily recognized by anoperator, thereby improving the workability.

The unit in which the splice reinforcing portion 50 is assembled to therear side of the ferrule 12 is detached from the assembling tool 370.

When the upward movement of the shaft portion 60 is regulated by theprotuberance portions 388 a, it is possible to easily detach the shaftportion 60 from the bearing portions 374 by deforming the side plateportions 386 in the direction in which both move separately from eachother.

According to the assembling tool 370, it is possible to accuratelyposition the first reinforcing member 51 with respect to the secondreinforcing member 54 and to easily assemble the splice reinforcingportion 50.

According to the invention, it is possible to treat the assembling tool370 and the optical fiber connector as an optical fiber connectorassembling set. The optical fiber connector assembling set may include aconstituent (for example, a pressing jig 393) other than the assemblingtool 370 and the optical fiber connector 10.

What is claimed is:
 1. A pin clamp used for an optical fiber connectorcomprising a ferrule that has a guide pin insertion hole being formed toreceive a positioning guide pin of an opposite optical fiber connectorand an optical fiber of which one end portion reaching a joint end faceof the ferrule is fixed to the ferrule and of which an other end portionextends from the ferrule, wherein the pin clamp, which is attachable toa protrusion protruding from the opposite side to the joint end face ofthe ferrule, being formed to secure the positioning guide pin in theguide pin insertion hole, and being detachable from the ferrule in adirection crossing the guide pin insertion hole, wherein the pin clampincludes a fitting recessed portion being formed to fit a protrudingportion of the positioning guide pin to regulate movement in a lengthdirection of the positioning guide pin, wherein the fitting recessedportion being formed to receive a protrusion of the guide pin in thedirection crossing the guide pin insertion hole, wherein the ferrule hastwo guide pin insertion holes including the guide pin insertion hole,the two guide pin insertion holes are formed on both sides with theoptical fiber pinched there between, wherein the pin clamp has a bottomportion and side wall portions formed on both sides thereof and a spacesurrounded with the bottom portion and the side wall portions on bothsides thereof serves as an insertion space of the optical fiber, whereinthe pin clamp has two fitting recessed portions, which are formed in theside wall portions on both sides, wherein the optical fiber is aninserted optical fiber, wherein a ferrule boot covering a portion of theinserted optical fiber extending from the ferrule is attached to theportion, and wherein the pin clamp is formed to insert the ferrule bootinto the insertion space.
 2. A method of assembling an optical fiberconnector comprising a ferrule that has a guide pin insertion hole beingformed to receive a positioning guide pin of an opposite optical fiberconnector, an optical fiber of which one end portion reaching a jointend face of the ferrule is fixed to the ferrule and of which an otherend portion extends from the ferrule, and a pin clamp that is attachableto a protrusion protruding from the opposite side to the joint end faceof the ferrule being formed to secure the guide pin in the guide pininsertion hole, and being detachable from the ferrule in a directioncrossing the guide pin insertion hole, the pin clamp includes a fittingrecessed portion being formed to fit a protruding portion of the guidepin to regulate movement in a length direction of the guide pin, and thefitting recessed portion being formed to receive and put out aprotrusion of the guide pin in the direction crossing the guide pininsertion hole, the method comprising the steps of: splicing the otherend portion of the optical fiber to a front end portion of an externaloptical fiber; and attaching the pin clamp to the protrusion of theguide pin so that the protrusion of the guide pin is locked to thefitting recessed portion from the direction crossing the guide pininsertion hole, wherein the ferrule has two guide pin insertion holesincluding the guide pin insertion hole, the two guide pin insertionholes are formed on both sides with the optical fiber pinched therebetween, wherein the pin clamp has a bottom portion and side wallportions formed on both sides thereof and a space surrounded with thebottom portion and the side wall portions on both sides thereof servesas an insertion space of the optical fiber, wherein the pin clamp hastwo fitting recessed portions, which are formed in the side wallportions on both sides, wherein the optical fiber is an inserted opticalfiber, wherein a ferrule boot covering a portion of the inserted opticalfiber extending from the ferrule is attached to the portion, and whereinthe pin clamp is formed to insert the ferrule boot into the insertionspace.
 3. An optical fiber connector comprising: a ferrule that has aguide pin insertion hole being formed to receive a positioning guide pinof an opposite optical fiber connector; an optical fiber of which oneend portion reaching a joint end face of the ferrule is fixed to theferrule and of which an other end portion extends from the ferrule; anda pin clamp that is attachable to a protrusion protruding from theopposite side to the joint end face of the ferrule being formed tosecure the positioning guide pin in the guide pin insertion hole, andbeing detachable from the ferrule in a direction crossing the guide pininsertion hole, wherein the pin clamp includes a fitting recessedportion being formed to fit a protruding portion of the positioningguide pin to regulate movement in a length direction of the positioningguide pin, wherein the fitting recessed portion being formed to receivea protrusion of the guide pin in the direction crossing the guide pininsertion hole, wherein the ferrule has two guide pin insertion holesincluding the guide pin insertion hole, the two guide pin insertionholes are formed on both sides with the optical fiber pinched therebetween, wherein the pin clamp has a bottom portion and side wallportions formed on both sides thereof and a space surrounded with thebottom portion and the side wall portions on both sides thereof servesas an insertion space of the optical fiber, wherein the pin clamp hastwo fitting recessed portions, which are formed in the side wallportions on both sides, wherein the optical fiber is an inserted opticalfiber, wherein a ferrule boot covering a portion of the inserted opticalfiber extending from the ferrule is attached to the portion, and whereinthe pin clamp is formed to insert the ferrule boot into the insertionspace.
 4. The optical fiber connector according to claim 3, wherein thefitting recessed portion is formed to receive the protrusion of theguide pin that has a large-diameter portion and a small-diameter portionhaving a diameter smaller than that of the large-diameter portion at thetip thereof, and wherein the fitting recessed portion is locked to thesmall-diameter portion to regulate movement of the large-diameterportion toward the tip.
 5. The optical fiber connector according toclaim 3, wherein the other end portion of the inserted optical fiber isspliced to an external optical fiber.
 6. The optical fiber connectoraccording to claim 3, wherein a holding protrusion that protrudes to theinside and that regulates movement of the ferrule boot in the insertionspace to the outside is formed in the side wall portions of the pinclamp.
 7. The optical fiber connector according to claim 4, wherein eachof the side wall portions includes a plate portion, the plate portion isvertically upright from a side edge of the bottom portion, the plateportion includes a fitting recessed portion and an extension, thefitting recessed portion is configured to regulate movement in a lengthdirection of the positioning guide pin by being fitted into thesmall-diameter portion of the positioning guide pin, the extension isformed to extend upward from the further inner position than the fittingrecessed portion, the ferrule boot is configured to be fitted betweenextensions that are provided at sides of the insertion space, and adistance between the extensions is substantially the same as a width ofthe ferrule boot.
 8. The optical fiber connector according to claim 7,wherein each of the extensions has a holding protrusion that is formedat the inner edge of the extension so as to protrude inward, and theholding protrusion is configured to regulate an outward movement of theferrule boot.